Well there are a number of ways a slave could serve in your line of work and most slaves are trained into servitude before they are sold so as not to fight for their freedom.
Slaves could serve any purpose really Maid/manservant, stripper/escort, Casino Dealer, Barhand etc... You could use them for many purposes really. Although I would suggest you do not put them in ranking positions they nay not understand. The process taken for loyalty training is not always healthy for the IQ.