One of the ways to remove the paint would be to shot blast it, but if you don't have the facilities to do that you could use a wire brush but you wont get a good finish, I would advise anyone not to do it though, the weight you lose is minimal, also its a lot of work to get it off with a wire brush, took an evening to do some break mounts. the paint on a bike is primarily to protect it, as soon as the paint comes off it oxidises, so although you can shed an unnoticeable amount of weight, the life of the frame will depreciate, try buying some lighter pedals or something, that should shave a bit of weight.