Re: Funk studies
Check out The Funky Beat - Garibaldi talks about the sound level concept, and gives a cool overview of some good ghost note/linear exercises and some great transcriptions of his famous grooves. It starts very simple, then gradually gets more complex (he even starts to get into some Chaffee over the bar/odd time stuff towards the end).
After that book, Future Sounds could be cool - that's an amazing book, but more fusion oriented than straight up funk.
Another book that's nice is Mike Clark's Funk Drumming...