The position doesn’t matter. It’s the amount of erection that’s important. Too much and you might injure yourself (and it won’t allow for blood movement). Too little and there won’t be enough blood to move under pressure with the jelq stroke. You should feel the pressure in the shaft and you might feel the blood rushing past your fingers as you move the stroke out from your body. However, you don’t have to feel anything for it to work. You just have to move blood under pressure at about 70 percent erection.
Feeling the skin pull is not unusual for new guys. Begin uncut should actually be in your favor since you probably have loose shaft skin to begin with. Just gather it toward the base as you grasp the shaft for the jelq stroke and use it to slide your grip toward the glans. If you can’t seem to get it with the circle grip (the “OK” sign grip) then you might want to try RB’s dry jelq method which employs the fingertips of both hands on either side of the shaft. You don’t worry about base clamping with that method.