Old undercoat residue

[Stillboardin]

In the process of stripping the undercoating off the bottom of my 68 Mustang and in some areas where it was on pretty good there are remains of the tar undercoat. I have tried heating it, using grease remover, wax and grease remover, simple green, purple power etc to get it off.

Is there something beside blasting that will get that crap off? And if I don't get it all off will the epoxy I spray just bubble off?

 

[Barry]

Take some urethane reducer and wet a rage and try it, if that works, then look for some MEK.