I have unofficially been doing penis bends for a quite some time, and not with my hands either. I first began wearing briefs when I got my first girlfriend because I wanted to keep my erections discreet. I continued to wear them because I liked the resistance they gave when I tried to get an erection. Everytime I would get an erection, my penis would have to conform to the shape of the briefs. It would be forced down and curved, like you see in the underwear models. I began watching porn with briefs just so I could feel my erection trying to break through the underwear. It would get so hard that it would only get forced down by naturally bending at the base. I noticed that when I took my briefs off, my dick was so engorged. I continued to just wear briefs and get erections for a year. I can’t rule out natural growth, but my penis grew a quarter (1/4”) inch in two months. My dick hadn’t grown since I was 18, and all of the sudden the briefs were bending my dick down and making it engorged and I had a bigger penis(!).
In summary, my penis was bending at the base everytime I got an erection in my briefs, because it was being forced downward by the underwear. I noticed my natural girth was much bigger, and I could just tell when I grabbed my dick. My fingers could no longer fully wrap around it.
This is very similar, in theory, to the manual excersize which has been promoted, in that the bend was making my penis larger.