Let me clarify my above response. I think it is a combo problem. Too much heat that gives you too much paint. I little of both will do you. Don't worry, everyone has probably had that issue when first starting. I did!
Just remember 4 seconds of heat no more and just swipe the jig in the powder to cover it and tap off the extra. done.
You will get the hang of it.
You can even try backing the heat of your oven down to 300 degrees. It will be fine.