Stripping this chassis down will be a faff so I've treated it to a brush coat of lovely Humbrol primer. I did buy a new pot, but only because I can't find the old one.
The sticking power of this stuff amazes me. OK, I've kept the metal clean but it does seem to work well. An etching primer would be better but I find the brushable versions too thick, and you can never clean the brush out afterwards. This stuff comes out with water - how it works so well is witchcraft.