Heavy deadlifts, heavy rows, heavy chins, heavy hammer curls.
Never use straps on anything. Ever. If double-overhand gets too tough during the set use mixed grip. Switch your mixed grip a few times when that gets too tired. Use hook grip when your mixed grip is too tired. Use chalk if you have too. No gloves either.
Farmer's walk with a combined weight of your max deadlift (so half your max deadlift in each hand).
Use a thick (axel) bar for deadlifts, cleans, presses, curls. Hell, use it for everything. For dumbells start using fatgripz or wrap then with a towel. Fat bars are a great way to build size and strength in the forearms. Thick bar reverse curls are awesome.
Hand grippers - CoC, AtomGripz, Heavy Grips...anything. They're pretty good for forearm size just don't over-do them.
Block weights are good, any sort of pinch grip lift is good too. Doing regular lifts with a vertical bar is fun also. The wrist roller is a hell of a workout.
After all that, then you can think about fiddly stuff like wrist curls.