I always used a mixture of baking soda to clean after tinning.Also use baking soda on the lead ,before filing. Agree the best is epoxy primer over the lead then filler
Do not use hardware store thinner.Most labels say do not use to paint.A unopened can would bring $300 from someone who needs it.Good quality thinner is available,I bought some at Hershey last fall.I think Global still has it.I used coach maroon on my 34 Very nice color