You brought up the point about being too close to the heating elements. How close is too close??? is there something to look for to say it is done or is a trial thing??? At what temp and how long is normal???
I started out powder-coating with a toaster oven and had difficulties that I attributed to uneven temperature distribution. I was getting excessive discoloration of copper that was too close to the top heating element. After a while, I broke down and bought a real powder-coat oven and my results improved dramatically.
A full-size oven, especially if it is a convection oven (without too strong a fan) would probably do much better than a toaster-oven. One advantage of a better oven is a more accurate thermostat. Many are off by 50 degrees or more. You might want to get a good oven thermometer to determine how to set your thermostat.
There is no particular look to a powder-coated piece being "done". It is a time and temperature thing. The recipe varies with the powder, and the directions should come with it. I've settled on a clear powder that flows-out at 320-350 degrees in 5 minutes and cures at the same temperature for an additional 20 minutes. I am not sure, but I might get less discoloration of brass and copper with this powder than one that flows-out at 400 degrees.
Regards,
Eric