Black Streaks (Under window) up date

Soft scrub is abrasive and can take the gloss off gelcoat, you want black streak off not paint, if coach is blue paint whatever you use has to be safe for painted surfaces. If you are going to use abrasives Barkeeper's Friend is the least abrasive product. I would go the cw store route and checkout more black streak removers without abrasives and advertised as safe to use.