Yeah I do it quite often. I actually learned the technique by watching my wife play with her clit. I use my middle finger and just work my frenulum until it builds up to the point of no return

Yes, I have done this through my pants with my dick pointing north crawling up my belly. Just subtly rubbing my frenulum with my thumb, even with other people nearby, but nobody notices. When I was younger I used to be able to cum this way and make a mess in my undershorts. Now that I'm an old fart, I still prefer some serious stimulation right there on my frenulum, but it takes a bit more effort to reach an orgasm, so it doesn't happen anymore just while sitting in a waiting room or something. I have to actually go somewhere like a toilet stall and pull my pants down and diddle myself properly

Yea. I think one time I did it in a car ride with friends and no one even noticed I was masturbating by rubbing my cock tip. I actually came in my pants. What fun

Yes I do it quite often especially on those occasions that I can't fall asleep

I did and I do agree. It is very intensive