Just to throw this out there Marty and Bill,you can smooth with filler before powder. You just have to use the correct stuff. This works well,
http://www.eastwood.com/hi-temp-lab-metal-24-oz.html
I have not used it, but a friend has and I have seen the results. Not bad at all. It can be thinned with solvent for spreadability and also smoothed with a solvent soaked cloth. This may be the route we go. Just thought you would both be interested.