My forearms get tight when I'm stressed or sleep deprived. I have one of those large "thumper" massagers (like the "Hangsun Handheld Neck Back Massager" on Amazon). When you use them, find the sore spot in your muscle very close to your elbow. Work that out with the massager.
Does it ever lead to tingling sensations in your hands? I was dealing with what I thought was cubical tunnel and noticed my forearms are always so tight
All sorts of vibrating things will make your hands go tingly after a while. But if you're talking about your hand on the arm receiving the massage, you should probably see a doctor about that before you cause yourself nerve damage.
I use it for my upper trapezoid. More recently I bought a fancier unit with independent electrodes, but I keep coming back to this unit because it's so much more convenient.