Prepping the Copper Board

Unwrap the Board

One suggestion is to use auto primer to make the paint stick the board better

Spray the Board

Next we need to spray the board.
The general view is that the more coats of paint the better, and that there should be at least 2 coats so that when removing the invisible layer left by the laser the smaller traces can remain on the board during cleaning

Paint Types

There’s a few different suggestions on the types of paint. The main two mentioned in the links are

There’s also

I’ve also got some black acrylic paint from WHS Smiths to try out (Humbrol). For black acrylic paint, the suggestion is to use 3 - 5 coats allowing time for each coat to dry.