Homebrew PCBs

I think considering the ease of use and the mess factor of using the powder paint or toner powder, it will dissuade one going that path.
As far as using the CO2 lasers the problem with paints and burning off paints is some of them leave a oily residue after burning up that is difficult to take off. It works for most applications but if you are making fine lines and want clean edges then you will want to use Asphaltum, you get it in craft shops or dickblick online. The power in a CO2 laser is adjusted by the frequency of pulses and each pulse is ON at max power. If the material vaporizes on a single pulse then no matter what low settings you have it will not work for melting and fusing.  
Keep us posted on how it goes.
Kim