Either solvent will work, just make sure you do an oil change since some of it is bound to get by the rings while cleaning.
I don't even remember where I got my brass scraper, but it came in real handy for the tough deposits. Short of that, a hard plastic scraper, even a homemade one, with a good edge would help the tough spots. Just be careful when scraping.
The brass brush in a drill should work, just go easy with it. Try it lightly in the center of a piston and see how it works. You're not going to need a lot of pressure, especially if the carbon has been soaking. I would try a brass hand brush first, and go to the drill if you find hard stuff.
My cylinder head overhaul: http://www.jeepforum.com/forum/f13/cylinder-head-r-r-picture-heavy-1348138/
My transmission overhaul: http://www.jeepforum.com/forum/f13/how-change-transmission-electronics-1560948/