In as much as bottom
paint is quite toxic, you would probably be better off doing it outside. Also it is not a good idea to let the residue soak into the ground. I would use a drop cloth to catch and contain the droppings. If you choose to grind or scrape it off where a high quality repirator. If you use chemical removers make sure to protect your skin. No matter which method you use, with all due respect to Mike, the job will take a lot longer than two hours. Then again the hardest part might be emptying your garage.
Good luck
Jeff