Blowtorch...welllll...
Jes' kiddin'...maybe not that extreme, but, the stuff is just awful. I won't have it on any of my boats unless I have to seal certain plastics and then the tube goes home immediately. Once you have scraped (or try Art's suggestion, I'm not familiar with it) all of the visible 'rubber' away, you have to eliminate all traces of the silicone chemicals in order to avoid 'fish-eyes' in your new paint job. The tried and true method is to thoroughly wipe down a two-foot circle around the fixture with acetone. The junk (silicone) migrates like you wouldn't believe. While you are wiping, continually turn your rags to clean areas and replace them frequently to avoid just smearing it around. It doesn't take much silicone (less than you can see) to spoil a paint job if you are going for high gloss.When working with acetone wear appropriate gloves and work in a well ventilated area. We used the stuff to clean our hands of epoxy and polyeurethane when I worked for a boat manufacturer. A lot of my old friends who did it often back then are suffering for it now...it is pretty nasty stuff regarding long term health issues.Best Regards,Chris