Im not sure what you mean by finding it hard to stay at 80 percent and can find it hard to not do a 100 percent erection.
Basically, here is what I do.
I jelq for as long as I want (i.e. 20-30 minutes or 500-700 strokes) at an erection level of about 40-60 percent. I feel that an erection level above 60% is mainly girth work and not really intended for beginners.
After jelqing, you can edge, which is whacking off until you are ABOUT to ejaculate. But before you do, stop for a few moments, then continue. basically, edging is whacking for 10-20 minutes WITHOUT ejaculating.
As for blueballs, Ive never got them. I almost ALWAYS whack off without cumming,
I just get to the edge of cumming, stop, and keep going until im about to cum again,
stop, and repeat until I dont feel like ejaculating anymore.
Ive heard that any semen that is "built up" will be easily cleared out when you take a piss, and will not cause any problems.
The argument for edging is that you get all those good sex-chemicals in your system, which can help with penis enlargement, as long as you dont ejaculate so that the "chill out" chemicals come and counteract them.
Again, Im no expert, this is just how I have interpreted theories on these forums. But as for blue balls, they have never happened to me, and I dont think its anything unhealthy.