Sorry I have no advice for length gains. I never made any attempts to get length gains. I can say however, I did gain in the length department, with wet jelqing at low erection levels. (they were newbie gains so take it for what it’s worth)
I don’t measure so I don’t know if it helps with length. Mro has claimed huge length gains from this exercise.
When I started doing Obends I did c grip dry jelqs along with my routine. Now that I got better with the bending technique I don’t jelq very much at all anymore. Mostly jelqing is to get the erection level right. Or to move the blood around keep things circulating.
The road to hell is paved with good intentions.