When sanding and working with fiberglass it is sometime difficult to evaluate how well the finish is. There are many color nuances from gel coat and translucent materials. You can get an idea from touch, but the best is to give it a quick spray of primer.
So that what I did. I didn't have any expectations as up to this point I have not used any finishing fillers only structural mixes (fiberglass cloth and flox, epoxy mixed with cotton flox).
The finish was surprisingly good, it will not take much effort to finish them off.