Electronic – How do PCB fabrication houses make PCBs

For tinning, my cheap home method is to coat the traces with a flux pen as soon as the board is finished etching, then run all over them with the thinnest coat of solder from my iron. I've drilled them before and after the flux and or tin process and usually prefer to drill before fluxing.

I too use tin snips for cutting my boards, sometimes sanding the edges with 600 grit wet and dry paper with water and a little soap to get a nice smooth edge.

Conformal coating is available to coat and protect your board. I'm planning to give polyurethane varnish a try on my next project.

Surely you can do soldermask, if you already mastered making PCBs using photomasks. Material for soldermasks is also UV-sensetive, so you expose & develop it and that's it.

But unless you are using reflow soldering at home :-) , there is no much sence. You can solder even small-mid size BGA's without soldermask - just flux & practice.

Or if you badly want soldermask for BGA in small quantity - you can just take capton material, and manually make all required holes and then glue it to PCB.