John:
First a suggestion.
Dont use your good parts to learn on. There is a learing curve with plating, especially potmetal. Get some copper tubing,buff it and plate that to start.
Then when you feel comfortable, do your parts.
As for potmetal, it is very, very finiky!
I sandblast my potmetal until all the chrome is off,(this also gives the next plate a nice fresh coat of nickel to adhear to.
After that I soak it in a mix of 75% water and 25% phosphoric acid. Clean it off with a small steel toothbrush and water until the areas that were dark are nice and shiny. Then boil it in distilled water for at least 2 hours. This will clean out any last acid down in the metal. Otherwise you will get blisters about a week down the road.
I dont know if the Caswell primer eliminates this step or not. Im working mostly with very pitted/deteriorated potmetal. Your handles look pretty good to start with.
After The part is clean I put a strike plate on it and then into the acid copper for about an hour.
Then you work it up from there.
Good luck and practice, practice, practice!!
48Buick
Then you can plate