I used to remove asbestos for a living. Even if what you've got has asbestos in it, I wouldn't worry about doing a bathroom. Keep it wet with soapy water as it breaks if you're really worried about it, but I wouldn't.
Heat will help. Scrape up what you can, a long handle will help, then use a heat gun on the tough parts.
What do you do if the mastic also contains asbestos?
