If you are going for 100% erection, the above post should be fine. But if you are going for less, don’t watch porn or what not to get to your erection level, as you may train yourself that sexual arousing situations = 80% erection, or whatever you are aiming for. Then when you want to have sex, you can only get 80% erection because you’ve trained yourself that porn (equating to sexually arousing situation, or having sex) equals an 80% erection.
This is just theory, but it makes sense to me.
Actually to take advantage of human conditioning, you can play some sort of stimulus (say a certain song) whenever you are jelqing. After awhile your mind will set your dick to your jelqing erection just by hearing the music. This also separates PEing from actual sex, so your body doesn’t go to the 80% erection or whatnot when having sex, as the music isn’t present.