Pictures would help.
I'd probably file it with a half-round ,I'll file, then sand it smooth and nice. Then refinish.
In general I'm not a fan of refinishing only one part of a bow. I don't think it's likely to blend well with the original finish. And I doubt it's worth refinishing the whole thing. Personally I'd save a bit of money over time, then sell the cartel and buy a bow that's made with a grip you like.