Ok, here is my hand/wrist workout
Get a dumbell you can take the weights off of. Put weights on one end of it(start with like 2lbs or less).
Excercises with this dumbell. Best done while sitting.
A. Grab the end without weight on it. Put your arm on your knee. With the weight up in the air rotate your wrist from side to side.
B. Same as above except the weight is under your arm.
C. Best done while standing, Hold the weight as in A. above, but while standing let your arm hand down and just pull your wrist up(like doing wrist curls).
D. Now lay down. With the arm out, weight towards head, push the weight up and then down(like a reverse curl of C).
A. I do wrist push ups. Basically just standard push ups with the back of your hands on the floor.
B. Finger push ups. Start with all five of each hand. Then 3(thumb, first and second fingers). Then just thumb. And then just first and/or second.
All of this isn't necessary(I'd say phase 2 can be avoided by most) but phase one will help with guitar playing
I also use a Hand Squeezer thing(not the goofy guitar thing you push with your fingers, but the hand thing you squeeze together). I use it so much I have to buy new ones every so often cause I wear them out
Disclaimer, these are tough excercises. Not to be taken lightly. Don't do what you can't do. BE CAREFUL