Knocking out the flash and filling the seams is practically voodoo - you need a die grinder and pro cutters to get it cleaned up.

The pre-zamac oxidizes instantly, it's a bit of a trick to get it clean enough to stay painted, but now there are good etch primers on the shelf generally available.

I've got my two favorite A-Bones - the Woody and Roadster PU to build. Would like to find a good source for authentic looking hubcaps vs slotted screw heads.