I found palm down makes the rest of my hand less obstructive, but maybe it’s all in the technique (?). I’d wait till shower time, and found doing light stretches first helped as a good warm up. With a palm down technique, I applied mild pressure as I jelqed. I would caution against death grips, but you certainly aren’t petting your unit either. As this site has advised many times over, look for physiological indicators (your body’s always telling you if something is wrong) to avoid over strenuous workouts or injury.
What I’m about to say is purely anecdotal but I found that if I could avoid masturbation after a good jelq session (which can be very tough), my penis remained swollen well after the procedure (without deflating like a balloon after ejaculation), and it was only then I began to see real progress (especially in length). I’m not suggesting to go “No-Nut November” per se, but just wait a bit, perhaps later in the evening before rubbing one out.