How to remove silicone residue from fiberglass tub?

http://homeguides.sfgate.com/removing-silicone-caulk-residue-28359.html

I would try a plastic putty knife ( metal might scratch if youre not careful) and maybe a hairdryer. Its a very tedious job some sources recommend a sharp utility knife Or thin angled razor.

See below

https://www.thisoldhouse.com/ask-toh/removing-silicone-caulk

Goo Gone

Home Depot or Lowe's

Id try rubbing alcohol. Soak a rag and let it sit on the yucky. Don't breathe it in using a large amount. Let it sit , should loosen it up to scrape carefully with a razor. Don't force, if needed ,repeat. I did it on a sink edge with silicone, worked with no problem. I left it on for 24 hours restocking the rag as I went. Didn't seem to bother the porcelain, like you I had tried everything else. Just go easy and check before you wet the rag. Like I said, be careful as u don't want to breathe it in when it pour on the rag. It seems to soften it and make removal easier. Someone suggested nail polish remover, but I know that removes enamel polish so I was worried about it marring the porcelain.

Tried that too

Thank you all..going to soak in mineral spirits and see if that works!

have you tried a new/sharp razor blade.

nail polish remover