It's a very good idea to paint the transformer cover and the actual metal stack of the transformer itself too. I take painter's tape and wrap a loop around the terminals so they don't get painted, then spray the transformer with black nitro lacquer. I would get a recognizable brand and avoid stuff like the Ace Hardware brand.
For the cover, I find it works well to clean it with steel wool and alcohol, then clear coat or also spray it with the black lacquer.
The chassis plate will look the way it does for a long, long time. When I get old brushed kits back, typically the aluminum is just dirty more than anything.
