As an older guy, I don't get as hard or as often as I want to. So I have used a penis pump for several years. Yes, they really do work, and can be a lot of fun to watch your cock start to grow bigger and bigger. Use a semi soft lube for best vacuum sealing at the base, as well as inside. Don't pump too strong or you may cause some blood bruses. I like to pump, hold far a few minutes, release, and pump again and again. It feels really good to hole at the bottom and pump your cock into the tube. A clear tube is best to watch the results.
I also enjoy pumping my balls and watching them swell one at a time into the tube. You do need a lot of lube for this. Dependind on the opening at the bottom of the tube or flexible ring at the base, both balls may get pulled into the tube. Not a problem, but it may take some care to get your balls out of the constriction. Just take your time, remove the flexible base from the tube with the balls around ans slowly work out one at a time. It does feel very good!
A pumping session should not last more than a half hour or you could cause some damage to the erectile tissue.
Then enjoy a good hard jerk off.