I shave in the shower with hot water and a Fusion manual and I still have to take what seems like countless passes in all directions. I don't get irritation, it just takes a while to shave.
I shave in the shower. It is the last thing I do. I wash, and shave my face and put my head in the hot water for a couple of minutes then shave my head. Leaving it to last gives my thick hair time to soften up and get warm. I rarely shave in the sink. (Wife says it makes a mess)
Sink shaver, here. And I go over and over and over, in as many directions as I need to, to get it to the point where I feel nothing but smooooth skin when I run my hand over my dome.