Use Omni MS-251 spray gun cleaning solvent. You can get it from your PPG auto paint store or other brands may have a similar product ( Spray gun cleaning solvent). It works good for removing RTV, 3M weatherstrip adhesive ( gorilla snot ) and aviation sealer ( Baby poop) from gasket surfaces too.

I should be a salesman for this stuff. Once you use it you will see..... The stuff work on everything.