Pumping is by far the best way to stretch the glans, but it's a little tricky.
Let me explain, but first some theory.
The penis is formed from three cigar shaped bodies. The corpus cavernosum, the two on the top and the corpus spongiosum, the softer one on the bottom. The glans penis is really just an extension of the corpus spongiosum.
Blood flows in to glans from the deep dorsal artery and arteries in the CS.
Blood mostly flows out through a network of veins around the top circumference of the base of the glans, the retrocoronal plexus. This drains in to the dorsal vein, the big vein on the top of the penis. There is also some minor drainage on the under side of the glans in to two small veins running along side the CS.
Normally the glans is at its largest right before ejaculation. Muscle contractions increase the pressure in the CS which in turn causes it to increase in the glans. That presses against the retrocoronal plexus, blocking outflow, further causing the glans to "flare" and usually triggering ejaculation.
If you want to stretch the glans you're going to need to force blood in to it and prevent it from flowing back out. That's tricky because of the massive network of vessels in the retrocoronal plexus.
What I've found is if I pump long enough and get the glans hard enough it will get big enough to stop the outflow of blood and continue to swell double or triple its usual size. Getting to this point has been elusive for me. I can do it maybe one in every ten tries.
But I believe I have finally discovered a method that works reliably. I pump in a 2.25" tube for an hour to an hour and a half. Starting at 6inmg reducing to 5 and then 4 after 30 minutes and 60 minutes. I use a thin ring, about a quarter to a half inch wide of stretched out bicycle inner tube just behind my glans. This helps trap the blood in the glans. Its important that the ring isn't too tight or it will block blood flowing in. I use estim while pumping to extend my election, an electrode just inside the urethera and one in my ass.
And it works. I can pack the tube with, my glans. And if remove the tube after about 90 minutes, put on a just barely tight cock ring behind my balls, the glans continues to expand. Usually for about 30 more minutes, either until I'm exhausted or I cum.
Now for complications. Pressure blisters are a constant worry, especially with a session that long. Over doing it will cause them and they can appear very quickly, within minutes. Because I'm using an electrode just inside my urethra if it is positioned wrong, pressed against the side of the tube and pulling down, it can cause tears, abrasions or bleeding just inside.
Tools I use: leluv brand tubes. Lots of sizes and they're completely clear. The ruler in some pictures is just a sticker that easily comes off.
An electric vacuum pump that can run constantly like the kind used to pull a vacuum for several hours on a car AC system. It's obviously much too strong so I pair the pump with a vacuum regulator used in health care. That let's me safely set the vacuum level much lower than the pump draws.
I also have a vacuum guage inline so I can monitor the pressure to the tube.
A hair dryer to warm the tube and remove fogging. Being able to see inside the tube is vital for catching pressure blisters.
Bicycle inner tubes cut in to short segments and used to make boots at the bottom of the tube. This prevents my balls from sucking up in to the tube which hurts after a while.
A homemade copy of a ET 312 estim machine, the mk312bt. A stainless steel buttplug for an electrode. A metal bead on a wire for the other end.
A 54mm ID ball hanger weight used as a cock ring.
