For jelqing purposes you should have and erection level between 30% - 60%. Less tends to lend itself into becoming more of a stretching exercise. That's because you aren't able to push enough blood up your shaft to really inflate your CCs or CS. Above 60% the person jelqing should be very well conditioned. The reason you don't want to be too hard is because now your CCs and CS are already nearly fully engorged and you risk pumping too much in which could lead to things like edema buildup. I think that masturbating is a decent plan for now, but in reality the longer you do this the less "excited" you will get. If you do beat off, will you be able to get at least to the 30% erection level? Things like not standing in front of a mirror, perhaps playing music and focusing on the music or a television program, etc. Let's face it, playing with your dick is erotic, and you need to train your mind that this isn't "playtime". While taking your mind off of the eroticism of jelqing, don't lose focus of the proper technique needed to safely jelq. You could easily bruise yourself for example, but if you aren't being watchful and continue to jelq, the bruise can be made much worse. Proper warmup is necessary to pre-condition your penis for the exercise. No different then lifting. No one is going to hit the weights without warming up first.