The District of Columbia government's experiment with holding "mass hirings" has been judged a success, at least where the practice was tried at two city hotels during the past year.

According to the D.C. Department of Employment Services, which assisted in throwing open the hiring process to as many city residents as possible, both the J.W. Marriott Hotel and the new Sheraton Grand Hotel have filled the bulk of their positions with people who showed up on widely advertised hiring days.

At the downtown J.W. Marriott, 495 people were hired, most as a result of an open hiring period held from late November 1983 through early January 1984, said Jackie Threadgill, a job agency spokeswoman. Salaries for the filled positions ranged from $3.55 an hour for waiters and waitresses to $11.70 an hour for hotel engineers.

And at the Sheraton Grand, which opened near Capitol Hill Dec. 28 and held mass hirings for three days in November, 210 people got jobs. Salaries ranged from $3.50 an hour for food service workers to $9.71 an hour for the senior maintentance engineer, Threadgill said.

Hundreds of job seekers lined up each time a mass hiring was held. Officials of both hotels and the job agency, which helped process the applications, said they expected big turnouts in a city that continues to have high unemployment.

The job agency is providing screening and referral assistance to about 40 hotels in the District, in addition to construction companies, consulting firms, restaurants, colleges and wholesale and retail stores.