The push up is one of my favorite upper body pressing movements. I strongly recommend the a perfect push up type of device in which you have handles (so your wrists stay tight and lined up instead of hyper-extended) AND you have a certain amount of "float." I mentioned the importance of this in Bret Contreras' recent push up article. This float allows your wrists to stay lined up while protecting the elbows and the shoulders. Cyclists use a very similar principle in their pedals; they have a few degrees of movement lateral and medial. This is extremely important in long term joint health. You can also use blast straps or visit your local rock climbing shop and get set up for less than $20 bucks. That's the set up I use; the webbing and carabiners have a breaking strength of over 2000 pounds.
Just don't make the mistake of doing that extreme twist like you see in the ads or some of the you tube videos. It's a subtle movement.
As for the wrist curls and extensions, my guess is the curls may help the hyperextension because the wrist curls will strengthen the flexors. However, the movement may also irritate the wrist complex. You're certainly welcome to experiment and get back to us. However, I'd personally use fat gripz or a fat bar (if you have access) for pressing. And don't forget about db presses with fat gripz attached.
And for movements such as lat pull downs, bicep curls, one arm rows, pull ups/chin ups, try foam pipe insulation cut to size. Depending on the size of your hands, you may need one or two on top of each other. The foam allows for each finger to sink in like custom molding. This, once you get over the learning curve, ABSOLUTELY will strengthen the flexor digitorum superficialis as well as flexor digitorum profundus. The former plays an important role in wrist flexon (the latter is the only muscle that flexes at the distal phalanges ie the finger tips). In other words, you can strengthen the wrist flexors WITHOUT actually performing wrist curls.