Hrm, well, ok. Even if he's not into crossdressing, all good maids need an apron. And find him a pair of cute male nylon briefs, that are like panties, but not quite. I'm sure as a woman you realize the difference in feeling between cotton underwear and nylon.
And you are right, everyone has different thresholds to cross when it comes to pain equating to pleasure. But you will know his reactions best, since he'll be under your hand!!
Still, I'd stick with some of the tried and true methods. Keep him guessing as to what/when is going to happen. Mix up the discipline with pleasure to heighten his senses (assuming he can go back and forth... not everyone can though). And don't forget your own needs either! I'm sure you are going to feel a bit randy at some point. It's every maid's job to ensure his/her employer is well taken care of. Do you have a little bell? You should use it to summon him, to get you glass of water, to pick up the pencil you dropped, etc. Oh... did he not get his cleaning task done within the time you allotted him? No excuses!!! Over your knee/the couch, etc! Present that bottom! If he's into any kind of role-play it could be quite fun to do this all day long. Well, maybe not for his bottom... but thats what Mistress's soothing hands and lotion are for right?