I find it easier to shave my balls when the scrotum is more tight than loose and hanging.
I just shaved today after work. I typically sit on a towel on the bathroom floor, leaning against a wall with a swivel mirror on a pedestal between my legs. I have a plastic bowl under the sink I fill with hot water to rinse the razor and use a wet washcloth to get my skin wet before applying shaving cream.
At first the hot water makes my scrotum relax but as it cools down it tends to draw up a little which actually makes it easier for me to get a good close shave. This position also allows me to shave around my ass and taint.
Sometimes I’ll shave in the shower but don’t feel like I get as close a shave.