Well I would suggest three things. Do pushups on your fists. May not seem like much, but balancing on your fist puts some strain straight on the wrist, which will help. Bicep workouts will also help, but switch them up. Do bicep curls, hammer curls, etc. By holding your wrist straight, you'll inevitably strengthen them. Lastly as mentioned, forearm workouts. Workouts which have movement directly in the wrist will do you the most good. Such as picking up and lowering a weight on a rope, which is tied to a bar. Summed up though, any working out you do with your arms, or carrying weight with your hands, is going to give your wrists more strength. Just keep upping the weight. Hope that helps.

Does he teach you at all?

It's not so much the strength in your wrists you need. It's knowing how to get out of them or at least counter.

Secondly, you can't strengthen your wrists the same way you strengthen your biceps. It's actually your forearms you may want to work on.

I kinda mess around with my grandpa submission wrestling but he just grabs my wrist and controls and submits me pretty easily and i have alot of knowledge of ground game. how do i get my wrists stronger so i wont get thrown around. he grew up on a farm and has the natural strength since he is full or almost full native american. i hate being ragdolled so somebody tell me how to get stronger in my wrists.