I'm following a program that really challenges these muscles, just started it about two weeks ago so obviously I haven't seen a difference yet, but boy do you feel it.
For the forearms it just consists of:
Wrist extensions, and wrist curls following a "321" tempo
(Take 3 seconds to raise, and contract your muscles 100%, hold for 2 seconds, low in 1) Do 10 reps of each exercise
For the shoulders, same thing:
Military press, and dumbell shoulder press following a 321 tempo
Dumbbell shrugs (behind you, on your side, and infront) 321 tempo
10 reps of each