Arduino is a very easy device to work with if you have any computer programming experience. If you don't, well.. as far as computer programming goes, it's not hard, but you'd have to learn everything from scratch. I don't think you would necessarily need it for your costume, since magma doesn't flicker.
Even if you do decide to use an arduino, I don't think you'd need to do all the PCB hacking that the fellow with the crazy equipment did. They make shields for controlling all sorts of LED's and other things.
Also, this stuff
would be fun for added smoke effects. Have a friend with a can or two follow you around, and when you attract a large group of photogs have them give a little spray for maximum flameyness. Maybe clear it with con officials first.. but the stuff is safe and barely has a smell.