I first started working with a Chemtronics pen - http://www.tselectronic.com/chemtronics/cw2200.html?tse_Session=8968b606d6be30ebbb1ca44798267d03
. Now i'm working with a Techspray brand pen http://www.intertronics.co.uk/products/tec2505.htm
. The techspray is FAR better than the first one I was reporting on. Old stuff was more flaky, had a wider tip, and adhesion wasnt as good. Not that it was BAD, but the new stuff is better. So if you want to draw traces, I recommend the Techspray brand.
Anyway, the stuff is pretty low viscosity and even with the fine tip, you have to be careful when drawing traces on perfboard or they'll bleed everywhere! You need the gentlest of taps. If it does bleed, you need to wait till it dries a little bit first (when it's more vulnerable to flaking off) and then scratch it into shape with a razor. But otherwise it's pretty good.
You can definitely follow a PCB pattern, as I am doing with the Tremulus Lune. You can also definitely solder to it pretty well at low heat. Not sure how low because they dont provide a number on the datasheet. Just to be sure I'm going over junctions with the pen again.
Overall, because of the pad-per-hole board, you end up drawing a surprisingly little number of traces. not bad.
Curing at 150ºC for 5-10 minutes increases conductivity too.
I dont know if I'll be able to show pictures, but I'll try.