Thermoplast resist for etching PCB

Since before I finished my RepRap I've been interested in using it to print the traces on a board and etch my own PCBs. The Wiki doesn't have a lot of information and the forum has none that I can find. Has anyone had good success with this and what process do you use?

Is it fairly simple to convert a Gerber file, or any other PCB software file, into an STL that I can use to print 1 or 2 layers onto the copper?

I've done laser toner transfer in the past but I think this may be a better way of doing double sided PCBs.

Thanks,
Gyv