So there aren't really any techniques that can be done while being fully erect?
Hi BTC, Answer is no, you could do yourself a lot of damage this way, just try jelqing and stretching exercises, for these just google pegym and look under exercises for beginners for both, this is not a quick fix way, it will take time, but some guys have gained up to 4 inch's, you can have a look at the photos on site, there's lots to look at on site and read.
Now if you go this way, just stick to the programs for how to and when, don't rush or push the programs, these exercises have rules just stick to them or you could end up with ED.
Do hope this helps you in your goal for PE.
Good Luck
Uuummm... just a hunch, this seems like a 'not right' thing to do. Maybe that's just me. Blessings - Blu