B&H Silver :)
I know they sound crude but they do get the silicon off. Remember this is on plastic thats about to be painted, not actual paintwork! Most of the lower end of the polishes and degreasing products contain petrol and noone complains. I've used these in the past when smoothing side strips, rear valances, etc and no paint ever peeled off. The dealers I've worked at in the past used brake cleaner to get rid of the sticky stuff and polish residue when sticking on new number plates...it works a treat.