he tricky part, Polly Holliday says, was teaching Dustin Hoffman the proper giggle. "I was trying to teach him to do this" -- she illustrates, tee-heeing skittishly behind a cupped hand--"but he had too deep a voice. We had to work on it a little every day." If the nervous titter with which Hoffman-as-Dorothy wards off a suitor in "Tootsie" sounds a tad like Holliday-as-Flo-the-waitress, that's the reason.

Hoffman and Holliday have been chums since 1975, when he cast her in Murray Schisgal's "All Over Town," her Broadway and his directorial debut. Then Hoffman went on to star in "All the President's Men" (wangling her a bit part as a secretary); Holliday settled into a five-year television stint as the wise and gum-cracking doyenne of the diner ("Kiss mah grits") in "Alice" and its spinoff, "Flo."

"I saw Dustin intermittently and he always told me that he hoped one day we could work together and I thought, well . . . " That's the actor's equivalent of "we must have lunch sometime." She was delighted to get his phone call last January asking for help with his new film "Tootsie" (it opens tomorrow), in which an umemployed actor desperately impersonates a woman to land a part. He decided to give his cross-dressed character Dorothy a gentle, hillbillyish voice rather like the one Holliday brought north from Childersburg, Ala.

For two chilly weeks, Holliday arrived early each morning at Hoffman's Upper West Side apartment for Pygmalion sessions. She prepared a sort of glossary, "words that I had trouble with, that are telling in an accent. All the sounds that people think southerners say wrong." Words like say-ownd (as in Puget) and ind (as in the bitter) and Duhstin. It was the same list she uses to ready herself for Yankee roles, and she drilled Hoffman on it over the course of numerous Scrabble games.

Mostly, though, they prowled New York. Hoffman pulled a ski cap down over what would have been his eyebrows if the makeup people hadn't already plucked them. Holliday wore the single thin raincoat she'd brought from California "and about 17 sweaters underneath. And we walked the streets -- across Midtown through Central Park. We walked for miles. He wanted to pick up my sounds so we talked, just talked about everything, politics, art, acting. I remember walking through the snow and laughing, talking about the weather and where we were going and the buildings and that man over there. It was a wonderful way to work on a part." Gradually, eerily, she began to notice her inflections and rhythms creeping into his speech. He appropriated one of her nervous gestures, too, an open palm clasped gracefully to the throat hollow as in (Holliday puts aside the omelette she's been lunching on to illustrate), "Why I had no ideah."

"He got so good so quick," sighs Holliday. A week into the tutoring she showed up at his apartment and was greeted by "an eye at the peephole. I thought it was the maid. I had this long discussion, explaining that Dustin was expecting me. She didn't know who I was so she kept questioning me. I didn't know it was Dustin until he started laughing."

She was not the only friend thus deceived. "He would just get further into it each day," Holliday reports. "At home, he'd begin answering the phone as a woman and seeing how long he could get away with it. One time he finally had to tell Murray Schisgal who he was -- and that's his best friend." Eventually, during filming breaks, Hoffman took to leaving the set in full Dorothy drag to try his moves on unsuspecting acquaintances. He accosted Jon Voight at the Russian Tea Room, Jose Ferrer in an elevator. He always passed.

The high point of Holliday's informal tutelage--she finds words like "coaching" presumptuous, insisting she "just gave him a little insight" -- was their production of "A Streetcar Named Desire," readings from selected scenes, one show only, starring Polly Holliday as Stella and Dustin Hoffman as Blanche DuBois. Another actor friend dropped by to serve as the audience. "Can you make it sound like I'm not a name dropper?" pleads Holliday, clutching her throat when pressed for details. The onlooker, it turns out, was Meryl Streep, at home in New York filming "Sophie's Choice."

For much of her 20-year career, of course, Holliday has struggled to shed the very drawl Hoffman was so absorbedly rehearsing. Arriving in New York after years of repertory in places like Sarasota, Memphis and Atlanta, "I had a difficult time for six months. Not only could I not understand anybody, but I thought everyone was mad at me."

The speech of Dixie, Holliday explains with complete seriousness, is meteorologically induced. "It comes from up here," she says, tracing two fingers upwards from the bridge of her nose, "and it's a result of the climate. When it gets real hot, it's easier just to talk like this" -- drifting up half an octave -- "than to work at getting it down here" -- from the diaphragm now. "It's laziness. I've never really gotten rid of my accent. I'll go home to visit my mother next week and I'll come back sounding twice as bad."

Although she's capable of consciously straightening her vocal curves until she sounds as neutral as Harry Reasoner, Holliday's natural speech pattern is Flo's, minus the brass. For the show, "I just made it stronger, goosed it up" until the proprietor of Mel's diner became May-ul. There's little physical resemblance. Holliday, who has come to lunch in an aquamarine cashmere cowl-neck sweater over beige trousers, is lankily elegant, with a sweep of silvery hair (she tells "Who's Who" she is 45) and delicate eyebrows.

In the year since Flo's honky-tonk closed its doors, Holliday's been working in television -- a Cheever story for PBS, a live drama for NBC, a CBS television movie. She donned a close-cropped wig and khakis to play a visiting major in two episodes of "Private Benjamin" while its star, Eileen Brennan, recovers from an auto accident. Unless that assignment continues, she has no immediate commitments beyond, of course, catching a weekend showing of "Tootsie."

Holliday had to fly back to California after her 'Enry 'Iggins stint and has yet to see her contributions on screen. "Oh, I can't wait," she carols. "I'm sure I'll be on the floor. Does Dustin giggle in the movie?"

Holliday's uncredited collaboration in "Tootsie"--"a professional courtesy," she demurs--became public only when Hoffman loyally alerted interviewers. She intends, though, to have him repay the favor sometime. She has it all mapped out. "One of these days," she muses, "I'll get a part . . . an actress from the South, in order to get a role, has to learn how to talk like a nice Jewish boy . . . "