I am in the process of starting a transom repair w/ Arjay and I want to add a couple of layers of glass to the inner transom skin (especially near the top) as reinforcement. The top of the inner skin where it meets the strong board is pretty thin and there are already a couple of small holes that I have to patch. I've started sanding the area to prep it for the new glass layers. The bilge area is painted so my question is, do I need to sand away all of the paint to raw glass or can some of the paint remain?

Hope this makes sense without pics.