I don't use Resist Pens at All. I computer draft my boards, Print off a Positive onto Mylar and use a photographic process to transfer the image to the board.
I bought 300 sheets (3 ft by 4 ft sheets) of Raw PCB at $1.00 sq ft. Good price. I cut these into 12 by 18 inch pieces and coat them with "Shipleys" Auto-Positive Resist.
Resist Pens are almost useless if you want Quality and the Iron On Transfers are good, but Too Expensive for production runs.
However, Almost Any reasonable resist will work in my Electro-Etch Process. If they stand up to Ferric Chloride, the should work OK.
For those reading this that maybe also interested in this process, Go to:
**broken link removed**
Take care.........Gary