I guess I should have checked this sooner but what I used was actually the professional version of the rustoleum. I attached the photo of the 2 products I used. I know 69charger says you do not need primer but I did my before this thread and used this spray stuff anywhere I sanded to metal. I never tried the regular rustoleum on this job but I have used it in the past. Lately I have only used the professional stuff in the spray cans because it dries much quicker so that is just what I grabbed when I picked up the gallon of flat black. Mine is extremely hard and the can says you thin with mineral spirits. I used the low odor mineral spirits for mine. To be purely scientific we now need Exit1965 to go buy some of the professional stuff and try it again using all the same steps! Sorry I did not check sooner but maybe our professional version is more like the Tremclad.
Todd