I just got some particularly stubborn glue from a number sticker off my frame with 91% alcohol. I use it regularly to clean the frame which has a really finicky matte finish. Always comes out great. I would be very wary of oils or solvents if the frame is matte. There seems to be more room for error with gloss frames.
As far as the helmet goes, I should probably clean the glue off mine before I post (what would attempt to be) an intelligent response.