Hey shabba, and welcome to the forum!
You´re not really supposed to move your hand along the skin of the shaft, because that wont work without lubrication. Instead you have to pull back the skin some, like on the down pull when you mastrubate, than tighten the grip with your thumb and indexfinger (or whichever finger you use) and slowly move up towards the head again.
You do this with a semi erect penis, I do it like 80-90% erect, other do it at about 70, whatever feels best.
Maybe you wont be able to do the whole penis in one stroke, because of the skin being too tight, just make a new grip and divide it into two parts then, or more if needed (but if you need more than two grips you probably have enough dick allready, if there´s such a thing ;) )
And you will feel the blood, start with just making a turniq grip at the base and hold that, then move slowly forward/upward, then you´ll get the feel for it. Don´t overdo the preassure at first, go easy.
Manual stretches, sure, better to stretch when convenient than not at all. I do that when I shower or visit the bathroom.