My experience with a household oven baking powder is, when you open the door the temp drops from 350 down to 200 and takes 7 minuets to get back to 350, then is when your 10 minuets start. I bake just about everything for 20 minuets. Also the thermostat on and oven varies a lot, when heating it may go to 350 and shut off, but the temp keeps rising because the element is still hot. When the temp is coming down, it my get as low as 275 before the thermostat kicks back on. I was having problems with the paint chipping, so I installed an electronic heat control switch to keep the temp at 350 constant or whatever I set it at.
On the bright colors like blaze orange I usually bake them at 375 for 20 minuets. I am not totally happy with the color after baking, but I thought is was because I spray electrostatic and it doesn't put on as thick of coat as dipping, and these colors look better if they have a white base coat. just some thoughts.