In article ,
says...
snip
Whatever you do - don't sand if it's tacky. You'll just clog the sander
(been there, done that). White spirit or petrol (or some other solvent)
may work - soak rags in the solvent, cover a relatively small area and
put some plastic sheeting on top to avoid evaporation. Leave for a few
hours, then scrape.

I suppose we might have expected a DIY Banter contributor to advocate
leaving petrol-soaked rags lying around the house ...