Not everyone succeeds, and so far, looking like Clint Eastwood has not rescued Garry Westcott from anonymity. Westcott has spent years trying to crack open the door of Hollywood wide enough to slip in, but you have to look hard to catch his successes: bit parts in "The Exorcist" ("I was at the bottom of the stairs when the priest came crashing through the window"), "Airport 1975" ("I stood next to Myrna Loy"), "Scorpio." He just played as an extra in the new Sylvester Stallone film, "F.I.S.T.," and the thinly-disguised movie about Aristotle Onassis, "The Greek Tycoon," both of which include some Washington scenes.

Westcott, 29, pays the rent by selling brass beds in Alexandria. You've seen him in commercials, selling Vantage cigarettes, Sheehy Fords, Hecht Company products and Riggs' banking services. He stays in D. C. to act in government films, which he says give him more experience than other hopeful actors collecting unemployment in N. Y. and L. A. Three years ago he spent $1500 to buy an unusual full-page ad in the show business bible, Variety . "There's just one gun bigger than Clint Eastwood's," read the copy next to Westcott and a blonde, "and Garry Westcott has it!"

Unfortunately, no one wanted it. Lack of funds prevented him from rushing to Rome to take up an Italian producer's offer to screen-test for some spaghetti westerns. Now he's writing a script for a cowboy movie set in 1916 that he hopes will feature Eastwood and himself as Eastwood's younger brother. "I have ambitions," he confides, "that could be considered unrealistic."