I live in a rural area with the usual subpopulation of thieves and meth-heads, and don't know anyone I would trust to come see my shop... besides I am trying to do everything myself that I can.

Today I decided to try soldering (having previously used 80 grit to bare metal). I used a propane torch, brush-on plumbing flux and lead-free solder (for its wider plastic range). I have many years of experience with electronic and copper-tubing soldering. Even so, it took me a few minutes to learn how to control the heat without dropping the puddle... took a few tries but I quickly got the hang of it and filled all eight holes.

Then I sanded them all down with 80 grit Roloc discs, went over the entire area with 220 grit on a sanding board, cleaned all the flux residue carefully with water and then grease & wax remover, dried everything and shot a couple of light coats of spray can etching primer. Even with a bright light at an angle, I can't see any trace of the holes