Internet told me that naphtha will soften the proflex caulk and then you use mineral spirits to wipe the naphtha off. I tried a little naphtha in one spot and it didn't really do much but maybe it would help to soften it with a hair dryer first. I asked a local old school RV repair guy and he just uses mineral spirits to soften the caulk. Naphtha is white gas commonly used as camping fuel in stoves and lanterns.
I *think* some plastic scrapers are better than others. I used to have one I got at plastics shop and it was great. I just bought one at Benjamin Moore and it seems like the blade's edge gets damaged/dulled too easily.