You can do some really weird affects with the new Mixer Brush in Photoshop CS5! That's the main tool I used for panel 4.
Incidentally, I finally solved my CS5 stability problems by putting a fresh version of OS X on a fresh hard drive. Turns out when your OS is an update of an update of an update (I'd been using the same hard drive since friggin' TIGER) it messes with your performance!
See you tomorrow.