I have a buddy that got into powder coating using a used oven and material and hardware from Eastwood.
He did my stuff for free, I paid for the powder, as practice parts to get his technique down. Did crank pulleys, engine brackets and worked his way up to valve covers. The last parts were really good and this is 10 years later they have held up fine.
One thing he found was, even though I was providing him with bagged clean - blasted parts, he would get better smother results when he re blasted the already clean parts just before powder coating. He may have started pre heating the parts prior to coating. No doubt there were other tricks learned. So if doing it yourself I would start with some practice parts. There are techniques to getting great results.