I'm gonna go ahead and be conservative and say "Don't do it." The boots have too many crevasses and bumps and knobs and whatever. It would be alot of work and you'd possibly be jeopordizing the most important part of your setup
I don't know how well paint would bond to polyethylene or polyether - may want to look into that - not to mention the chances of the paint wanting to crack due to constantly flexing the boot?
yo dude i would most definatey die that shit. your bound to have a much cleaner looking, better finished product. i used to do it to my lax heads all the time and it would usually turn out pretty nice when done right. and you can like write shit on it with a hot glue gun then after you die it you peel the glue off to reveal a nice message of your choice. it was just an awesome old time