Self-leveling compound/underlayment over painted floor

I’m in the process of prepping the floor for a basement bathroom buildout and I’d like to apply self-leveling compound to flatten out the floor, but a portion of what will become the bathroom floor is painted. It’s in great shape (probably 1950’s vintage epoxy paint) with no peeling or other defects. I’ve received conflicting information as to how to deal with the install – everything from just priming it with the SLU manufacturer’s primer to complete removal of the paint by either grinding or chemical stripping. Would scarifying the painted surface with a belt sander and an extra course belt do the job (i.e. rough up the paint and expose enough of the concrete surface for the primer to adhere or do I have to take the surface completely down to bare concrete? Any other options? I’d love to hear from a tiler that’s run into this sort of situation before.