Plastic shrinks when it cools, usually, print come loose when you cool down the build plate. If you print on glass, you could put the plate with print in the refrigerator.
If you can't put the build plate in the refrigerator, wait for the plate to cool; the print part sometimes pops off, if not, prying up a corner with an artist palette knife or a razor blade scraper will be enough to pop the print off.
Note that release agents can be used (from experience), but not what you suggest. E.g. when you print PETG on PEI it almost fuses, to release those prints you can use 3DLAC or any other PVA based spray or glue (which normally would increase the adhesion!) to be used as an intermediate less sticking release layer.
Do note all the questions here of people not getting the filament to stick to the build plate, do not grease up the plate, else you won't have a print to get off!