Speaking as a professional mechanic this is by far the most used tool during a brake job aside from my impact gun. Do your normal remove the tire and caliper bit, then remove the outer brake pad and insert this tool. A couple of firm squeezes and the caliper is fully compressed. And the best thing is that it will save you time. For a mechanic, anything that will save you time and effort is a definite win. If you get a chance to buy one of these, you won't be disappointed. I purchased mine from the Weekly Tool Guy that stops by our shop , But you can buy yours online from several places.
Just Google "Lisle Speedy Brake Pad Spreader"