I've used the dry film solder mask and think it's great stuff. I found it from a European supplier as Dynamask 5000. You'll need a laminator, the same UV exposure as you'd use for PCBs (if you make them that way) and some sodium carbonate to develop it.
I ordered a fair bit - probably more than I need. If anyone in the UK would like to try it out then let me know and I'll send you some.