Wilbur Mills wandered through the front door of the Longworth Building about 30 minutes before Senate and House conferees resumed work on the tax increase yesterday, and the huddled knots of lobbyists and congressional staff members parted respectfully to make way.

Mills continued across the marbled foyer of the building he once all but owned as chairman of the House Ways and Means Committee, then disappeared into an anteroom where only members of Congress (and former members) are welcome. It is not recorded whom he saw there, but Mills said later, "I have a number of clients and so far it's going all right . . . . They're nice to me here."

Attempting to kill an 8-cent-a-pack increase in the cigarette tax, Mills was just one of many former congressmen among the lobbyists thronging the Ways and Means Committee room to watch and offer advice as the conferees -- sometimes in public, sometimes in private -- wrestled with the bill.

Lobbyists, some with very expensive hourly rates, lined the hallways leading to the committee room. They buttonholed congressional staffers, checked notes with each other and talked to the lawmakers. But mostly they just watched and waited. "There's not much you can do at this point," said one.

"I just came to look," said former Michigan Republican congressman Jack McDonald, kidding no one. "I've been living this bill for three months and I didn't want to leave it now." He had been watching, he said, on behalf of American Express, interested in preserving the deduction for three-martini lunches, many of which are charged on American Express plastic. He appeared to be a winner on that one, but he was obviously worried about something as he buttonholed a staffer and pulled him into a corner for a private conversation.

Then there was Bob Duncan, former Democratic congressman from Portland, Ore., and a former chairman of the House Appropriations subcommittee on transportation. Duncan was representing a mass transit district and loggers who take out their timber by helicopter.

Mass transit wanted -- and apparently won -- approval to use tax-break leasing to buy new transit vehicles, as New York City is doing. The helicopter loggers wanted -- and apparently lost -- an exemption from the jet fuel tax that will go to the aviation trust fund to pay for the new air traffic control system, among other things.

"Farmers have an exemption" from the aviation fuel tax, Duncan growled, "and I don't see the difference between growing corn and growing trees."

One out of two ain't bad.

"Yeah, but I wanted 'em both," he said. "Maybe we can get it back later."

The crowd wasn't all former politicians, however. Phillip J. Burnette, for example, president of the Vrain Corp. of Martinsville, Va., said he was there to work for the tax credit that goes to firms providing jobs for young, disadvantaged people. Vrain trains beginners for the textile and furniture industries, and the tax credit means Vrain has places to send its graduates.

Standing in the hall, talking to staffers and lawmakers, is the way the system works, Burnette said. "It's one of the few systems where you actually have a chance to influence actions."

A senior lobbyist for a major corporation, who asked not to be identified, said the most important thing at this stage is to keep track. "We've really got to watch everything. My clients don't directly care about the cigarette tax, but if that is defeated then the conferees are going to be looking for more revenue, and we don't want them to come after corporate preferences. So we watch."

As for Mills, he said the way tax bills are done these days--in open meetings instead of behind closed doors--has done nothing but "open up the process for the lobbyists. Look at all these people," he said, gesturing at the mob in the hallway. "The public's not here, and what's open about all these caucuses going on around here?"