What cleans butyl tape off of rubber seals?

[Mark N.]

The factory left a big blob of butyl tape smeared on one of the top seals of one of the slides. It is causing that seal to stay folded under itself each time the slide is extended out, plus it is smearing itself onto the rubber roof. I tried cleaning it off with both mineral spirits and denatured alcohol to no effect. It simply smears along the rubber seal like warm chewing gum. I rubbed and rubbed and rubbed, but only succeeded in spreading it thinner, but not removing it. So, what the heck acts as a solvent to this stuff that won't harm the rubber seal? I'm thinking of trying a rag sprayed with brake cleaner.
On a related note, once I get the seals all cleaned, I am going to spray them with silicone on both sides. I am assuming the silicone overspray won't hurt my rubber roof? It would be darn near impossible to spray both sides of the seal without spraying some roof rubber too. Thanks.