ride. have fun. (and have a pretty high level ) If you are going to ask someone for sponsorship, don't start out with "can i have a free bike". ask them if they can give you some good prices on stuff.
i don't know any other way than grinding. but mabye if you use some fine sandpaper and just rub away the colour? the sidewalls will be a little 'rougher' than normal, but it'll not work like a grind I don't know really.