Hey guys! I decided to do the fiberglass work in 2 parts. First, I'm going to fill all the holes in the existing piece. Then I'm going to put a thin layer of fiberglass over it, to bind everything together.
Today, I did the first part. Here's how I did it. First of all, I stretched some painter's tape across the holes. Then I mixed up a slurry of resin and glass powder. I added glass powder until the resin was the consistency of peanut butter. And I used that stuff to fill all the holes. See photos below.
I'm going to let it cure overnight, then do the other side tomorrow. The resin won't bond to the tape. So tomorrow, I can tear the tape off and get back to work.
I should also note that I scored all the surfaces with sandpaper and a small file. You need to rough up the surface, so the resin can stick to it. Also, this "phase 1" will need to be sanded before I apply "phase 2", so they can bond together.
BTW, I put a garbage bag on the work surface, to catch any stray resin. It saves me the trouble of grinding it off later.