There was an article in SWS about this, all about customizing rubber lures, I think the guy in the article said make a clean cut with a razor blade and use some super glue. I don't remember if a specific brand was mentioned though.
Not targeting bluefish, but tell that to the bluefish.
The hot butter knife idea is interesting. I've found that the glue requires that the rubber be dry and it tends to stiffen the rubber in the areas of application.