Trying to determine the proper use of Weld Thru Primer. After the weld would the remaining exposed Weld Thru Primer be removed before application of epoxy primer? Also copper vs galvanizing-which is better for a particular situation? For a cavity that will be sealed such as a rocker panel is weld through primer correct to use inside or where would the transition to Weld Thru Primer take place? Or should I even use Weld Thru Primer at all?