You should really wrap them for bench. Bench is not a wrist exercise, so don’t use it as one. My wrists are really loose, even with strong forearms. Always been that way. I wrap them for anything over 315.
If you want some quick and dirty forearm work I would suggest BamBam levers and Thors Hammers. They don’t take much time at all will hit your lower arms in all directions. Good for grip as well.
I also built a great little levering bar out of pipe and a handle bar grip. This is spectacular for working one arm at a time.
One 8" piece of 3/4" pipe with the handlebar grip on one end.
Screw on a 135deg (approximantely) elbow to the other end.
Screw 4 or 5" piece of 3/4" pipe on to the other end of the elbow. This will be where you load your 1" holed plates. It won’t take much weight. Get a 5, 2 1/2, and 1 1/4lb plate and you will be set.
I sliced open a short piece of rubber hose and used that with a hose clamp to secure the plates on there in lieu of a collar.
This works much better than a straight piece of pipe as is doesn’t deload at the top portion of the levers.
Lever in 4 different directions. Inside out, outside in, reverse curl, and curl (standing up).
Your lower arm strength will skyrocket after a few weeks of doing these on a regular basis.