Having done this myself I can say that it works well but it is very dangerous!! If not protected by something, the brake pistons or master cylinder pistons will pop out and can fly across the shop and spray brake fluid all over the nice car in your garage or if you are really unlucky, they will hit you in the head. Wrap an old towel around the caliper or cylinder before applying air to it. Or use the grease gun technique-adapt a fitting to allow you to use a grease gun on the caliper/cylinder. Pump full of grease and the piston will come right out-and usually not fly across the shop either! Eric