Do you use both hands, or can you use just one hand and get the same results?
By rock hard, do you mean WHILE you are doing it, or afterward you will find your erection will be rock hard without touching it?
Thanks in advance.
You can use one hand and get the same results, the thumb on the top of the shaft is the most important bit.
After a while of erect kegelling, the dull stretching pain will be felt everytime you kegel and because you have slightly stretched the tunica the erection seems to feel much harder. Unless you have also been edging it does require stimulation to keep it at its hardest.
I try to aim for this feeling but it usually takes more than 20 minutes of jelquing and kegelling.