Personally (only slightly off topic) I don't think any sex-play should be used to punish a real transgression.
If that's a huge turn on for either party, then incorporate it into a role-play. Nothing wrong with the reluctant _____-girl getting ass-fucked by her ______-lord for spilling his wine (or whatever.)
But not in reality. Any physical punishment I wield would be something she truly dislikes and I take no pleasure in doing. Otherwise I'd end up looking for excuses to punish her and she would come to despise me, and rightfully so.
Anything she dislikes (but isn't a limit) which she knows I like... well she gives me that willingly. I get both the physical pleasure and the knowledge she does it solely for my pleasure. She gets to revel in her emotional submission doing the unpleasant task for me. (Does that make sense?)