[48Buick]

John:
When the potmetal was initially plated, this was most likely the process.
cyanide as a strike plate
nickel plate
chrome plate.

So.........if you strip off the chrome you will see that you go to the nickle plating.
In some areas you may likely go down to the potmetal.
Either way you will want some type of a initial strike to put on the potmetal so you dont eat it up in the acid copper bath.
Im not familiar with the potmetal primer but it sounds like a electroless nickel to me.
I personaly use a cyanide copper strike and have also used a High sulfate nickel bath on the potmetal.
You will have to protect that potmetal with some kind of a strike though.
Then you can plate with copper and fill your pits with solder.
After sanding and smoothing, go to your nickel and then the chrome.
Hope this helps
48Buick