SANDING THE BOARDS

With a nicely filled glass mat, the surface won't be perfect so it's time to become friendly with your sander.

A random orbital is perfect for this, but 120 grit wet and dry will do if you want nice muscles.

Here the board on the right is fully sanded the one on the left has clear imperfections. Click on the pic for a better view.

Both will be sanded to a nearly perfect finish, but not so aggressively as to remove any glass.