Years ago i invented a little device
Take a strong condom and fill it with water as warm as you can stand and then put that over the erect penis

work that for a while and keep adding a little hot water to that "
the heat makes a lot of difference and it is fun.
Shower stall or outdoor shower please!!

I am more interested personally in penile health causing a secondary/ primary result of more growth hormones than sex strange as that sounds
once the use of the penis gets into action the body resleases growth hormones of all types.
I also suggest weight lifting during and after penile stimuation

It is incredible your body is hyped up by the hormones and you lift 25-40% more weight during an enlargement /session.
Arnold Schwarteneggar said on Oprah that the pump of weights was better than orgasm!