Try this
Maybe ask the guys here on the reps and weights etc but my male friend once used this program for his forearms
Hammer Curls: 10KG (Left) 10KG (Right) 6 X 10
Wrist Curls: 9KG (each side) 6X 10
Reverse Wrist curls: 9KG (each side) 6X10
He did the exercises twice in a 7 day training week