(And often some antiseptic cream: my skin is insanely sensitive.) It fades gradually over about an hour, for me. I massage in some Vitamin E cream into the reddened flesh.
People advise you not to pump so hard your breasts turn red/purple. Or, you can cause small blood vessels to break and cause spots or even bruising.
Covered in a TV (hah!) news report, the multi-thousand device was connected to an electronically controlled pump, and had a harness for holding it in place. Jump forward many years, as I stumble over news of a suction device that women could use to enlarge their breasts. I discovered that by carefully halving it, with a touch of baby oil I could make it suck onto my chest, to give me two small bumps to fantasise with. And as part of that, to help my imagining along, I happened to have a smooth rubber tennis ball. I began imagining what it would be like to have breasts around the time puberty kicked in.