One of the biggest problems for service industry workers is that many forms of direct action, such as Slowdowns, end up hurting the consumer (most of them also members of the workering class) more than the boss. One way around this is to provide better or cheaper service -- at the boss' expense, of course.
Workers at Mercy Hospital in France, who were afraid that patients would go untreated if they went on strike, instead refused to file the billing slips for drugs, lab tests, treatments, and therapy. As a result, the patients got better care (since time was being spent caring for them instead of doing paperwork), for free. The hospital's income was cut in half, and panic-stricken administrators gave in to all of the workers' demands after three days.
In 1968, Lisbon bus and train workers gave free rides to all passengers to protest a denial of wage increases. Conductors and drivers arrived for work as usual, but the conductors did not pick up their money satchels. Needless to say, public support was solidly behind these take-no-fare strikers.
In New York City, I.W.W. restaurant workers, after losing a strike, won some of their demands by heeding the advice of I.W.W. organizers to "pile up the plates, give ‘em double helpings, and figure the checks on the low side."