Detroit makes cars, Pittsburgh forges steel and Des Moines grows grain. But in D.C., the home-grown product is paperwork. Lots of it:

Something like over 3 million pounds of paper go annually to the General Services Administration to be transposed into Federal Registers, congressional reports, memos and correspondence. That makes for a heavy load of reading for the people who make Washington tick.

And how do people in the Capital cope with these gargantuan quantities of registers, records and reports that spew off the printing presses daily?

Bill Hart--director of the White House News Summary prepared daily for presidential eyes, Cabinet officials and senior staffers--drinks in newsprint the way some people gulp morning coffee. When working the graveyard shift (midnight to completion at 6 a.m.), his night begins with a thorough reading of newspapers and a scanning of four wire services and a computer system. Around 4:30 a.m., another slew of newsprint hits the White House newsstands, which he'll skim.

Admitting that he has developed his "own little system" for getting what he needs, Hart looks for key words. "Reagan," "Administration," "Haig," "Weinberger" and other top official names attract his attention instantly. "So far," he says, he has heard "no complaints" from his summary's exclusive readership.

Other Washingtonians have, however, taken another tack and attended formal instruction courses developed to hone speed and reading-comprehension skills.

Sen. William Proxmire (D-Wis.) signed up in the early '60s for Evelyn Wood's "Reading Dynamics" course in order to get through all the tomes of hearings and the Congressional Records. He wanted, he says, to keep pace with "the really bright people like Hubert Humphrey, Wayne Morse and Paul Douglas that I admired very much" who "were all naturals" (at speed reading).

"They said to practice an hour a night; I practiced two hours and it really paid off. For instance, I read Jack London's 'Call of the Wild' in three minutes . . . it was just like watching a movie going in fast motion.

"You look for the forest instead of the trees," says Proxmire. "You get a better comprehension and you have the ability to read more."

Dr. Eugene Fischer, director of the Veteran Administration's Dental Program, says that because he used to "lumber along and laboriously plow through" reams of materials he turned to Transemantics. "In a nutshell, I found the course valuable for skimming, scanning and reading purposefully. I've eliminated a lot of minutiae not relevant, and find I'm taking less work home at night."

General philosophies and training vary, of course, with the rapid-reading instruction chosen, but many have overriding common threads:

* Unlearning. The basis for many courses focuses on getting rid of bad habits acquired in first grade. Instructors claim that because we learned initially by reading aloud, we've carried over the mental process of reading every word. Reading for speed deals instead with comprehension of groups of words and phrases at the speed once used for only one word.

* Previewing. If you're reading a report, you'll be trained to take in an overview by first looking at chapter headings, charts and diagrams. In some cases, you'll be urged to read the material over quickly several times instead of once slowly.

* Top and Bottom. Sometimes the necessary information can be gleaned by reading just the first and last paragraphs.

* Different Techniques for Different Materials. The courses have you pace your reading according to your familiarity with the subject matter, i.e., you'll be able to read through faster if you have a previous knowledge of the subject matter.

* Extras. Some courses use machines during the classes; others teach use of finger or pen as a page-tracer.

Is all this too good to be true? Can you kick up your heels after taking a course to improve speed and comprehension and use that extra time to get in a quick eight holes on the golf course?

No. You must think about what you're doing and concentrate constantly.

"We teach behavior-modification and work on changing attitudes and habits," says Harriet Brill, director, Reading and Study Skills for Transemantics, Inc. Learning the skills requires "work and discipline and it's not easy, You've got to constantly remind yourself (to do it properly). It's easy to become lazy."

Practice and constant use is the key to getting it down, says Brill, "like going on a crash diet. If you lose it in two weeks, you'll gain it back in two weeks."

The need to work at it daily is reinforced by Frank Agardy, president of Evelyn Wood Reading Dynamics, Inc. They'll allow you to return to classes tuition-free (there may be a charge for new books) for a lifetime to polish skills and learn new techniques.

"Reading dynamics is very much like tennis," says Agardy. "You don't lose the skill, you lose the coordination."

Speed-reading's detractors say it isn't reading, only skimming.

Woody Allen has said that he took a course, "learning to read straight down the middle of the page and I was able to go through 'War and Peace' in 20 minutes. It's about Russia."

And it isn't for everyone.

According to Sen. Proxmire, his wife Ellen says it ruined the relaxation of reading. When she read for enjoyment, she'd feel a little guilty about not reading faster.

But Agardy says that's okay; you can have your speed and ignore it too. "There's no such thing as being locked into one mode," he says. "Speed reading does not interfere whatsoever with conventional reading habits, it simply allows you the flexibility of reading at a much, much higher rate when you desire to do so."

At the other extreme: TV's "Saturday Night Live" once introduced the "Evelyn Woodski slow-reading course," which included this testimonial:

"Sure, I was skeptical. I think everybody is. But believe you me, I can now read 10, maybe 12 times slower than before . . . I never used to laugh when I read Mark Twain. But now that I take my time, I find him very funny."

But if it's a budget report you have to get through, and not Mark Twain, proponents say speed-reading can help.