Lead is a major problem with restorers. Some restorers because of past problems grind the lead out and replace with glass.
I hate that!
The reason they had problems in past is because of the following applications:
Treating with ANY acid.
Using acid etch primer.
Using lacquer primer.
Using 2K primer.
Using DTM primer.
None of the above will last long term.
1)DA the the lead with 80 grit, just to smooth.
2) wash with waterborne or solvent type wax and grease remover. Let set at least one hour before applying your epoxy.
3) Apply one coat of epoxy and let set 30 minutes before the second coat is applied. Do Not puddle or try to fill with the epoxy.