Im not sure what u call it but I like the one with a rope on a handle and weight on the end. twist the handle forward to wind the rope up, back down then wind back up the reverse direction then back down. It can give a good burn with the right weight and going slow.
We use to do this in baseball when I was in high school, builds forearms pretty good.
I work my forearm everynight
Haha na just kidding lol
Here what u have to do ,
Pullup hold for 50sec
Do it for 5rounds
Here is another one go on youtube and check athlean-x they have a video called 70rep (who dropped the bell) it's really good for ur forearm and ur core
When doing bicep curls or pull ups hold the bar with someting thick like a folded shirt. This will work your forearms.