30 year old undercoating might be a big pain in the @ss. Try gasoline first & then acetone.

 

Thanks for the suggestion. Still struggling to hit this gem with Acetone. I think I will worry about it in the spring. Getting ready to store for the winter.

 

I thought you were going to share an Update.

Oh well, Let her hibernate.

 

You might also consider paint thinner or mineral spirits. Those two should both be less powerful solvents than Acetone but might still work. Lacquer thinner will be one of the stronger solvents, followed by Gasoline and Acetone, then Paint Thinner, and some weaker solvents would be mineral spirits, keytone, or denatured alcohol. If I were you I would start with a weaker solvent first and let it soak for a couple hours and see what it does, if it doesnt do anything move to a little stronger solvent, and so on. Better to start off with something too weak than too strong...You can always move to something stronger if it doesnt work but its hard to move backward if something is too strong.