Let me say first that I've been at this a while, so my erection is fairly well conditioned.
I jelq at high erection levels and lower. I do my main jelqing after I edge. I do some edging every evening, trying to ride the 90% erection level. I will get up to 100% at the end, do a good hard kegel to get it full, then stop.
Then as the erection subsides I will jelq. Usually starting at 80-90%. I do slow jelqs to try to get the thing fully expanded. I use a grip firm enough to get good expansion.
I do 40 jelqs at this point, using over hand grip jelqing downwards at an angle.
By the end of the set I am usually down to a 70% erection. (But at times it will stay at 80%. )
I then do 50 upwards jelqs. My grip is less and I do it this way to just get an even workout.
Then I will be at 60-70%, and do 60 jelqs straight out from my body. Generally by the end of these there sets I am at about 50% erection.
That being said, I believe that jelqing at high erection levels is not best for good results. I have noted that I feel better when I jelq at 70%. It seems to work better. But like a lot of people I have a hard time staying at 70%. Either it subsides too quickly or gets too hard. By starting from an erect state and working backwards, so to speak, I am able to do more at t he 70% level.