Electrical – this small unconnected solder blob on this PCB

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.

Try 'Epoxy Ink PCB Screen Printing' in your favorite search engine.

Here's one source, and the ink description gives away the desirable properties regarding substrate supported, adhesion qualities, curing process and immunity to acid/alkali treatment.

Du-Pont PCB silkscreen inks

Nazdar

Another co. I had never heard about

PS: No personal experience with those. For low volume usage, and DIY silk-screen, I believe people have used inks used for ceramic painting, which need to be cured at high temperature.