Home DIY

I see. How one with nylon bristles? Or those 'poly abrasive' discs?

I will spend the time down there if I have to, but have a long list of stuff that also needs work (like pulling down that ceiling and finishing insulating under the floor).

Best I can offer you is try everything available - grab some cheap rotary brushes and test test test!

You could also try a brass brush and a heat gun, might blister it enough to make it easier to remove.