Homebrew PCBs

OK team, I have an Epilog Helix laser (http://www.www.epiloglaser.com).  While this can't etch the copper off a PCB, it can do a very nice job of etching coatings off of copper, down to a VERY fine resolution.

Question is:  What could easily be used to coat a copper clad board that will be resistant to the etchant (pick your flavor).

Ideally, the coating could also serve as a solder mask, and the process could go something like this:

* Coat the copper
* Reverse lase the board to remove the coating
* Etch
* Optionally re-coat (or clean and coat with a different substance)
* Lase to remove coating from copper pads

Any thoughts?

John R.
Beaver Dam, WisCOWnsin