Newbie here.  Is it customary to tip independent providers over and above the donation?

any $ tip. Some guys will bring a present to a lady, especially if she is hosting him at her incall location. Whatever you do, don't make the gift obvious like taking a nice flower arrangement in through the front door of the Marriott. Be discrete.

This ones from 5/13. Try to use the TER search feature, you can search by subject/keyword trust me, there aren't to many newbie question that haven't been asked before.