skin back for me - better aim control. But there are times I like to balloon my skin out with pee, holding the end shut - makes for an interesting look.
I like to do this as part of my warm up before finger stretching in the shower. Best in the morning with a full bladder. The best technique I have found is poking my pinky into the funnel and then take the other hand with forefinger and thumb clamping the foreskin tight around the pinky. This allows me to clamp just the tip giving me plenty of overhang left to achieve a huge balloon. I will hold it as long as I can before expelling and then repeat. I can get about 3 full sessions before my bladder is emptied.
Before my adult circumcision at age 33 I used to always retract my foreskin before peeing. It’s how I was taught and it kept my foreskin soft and supple.