squeezing tennis ball would help or stress ball or those thing with the spring. most of the muscle that control your fingers ar at the forearm.
i used to have a broken broomstick, tie it with a rope in the middle. at the other end of the rope hang a 1.5l(make it 2 bottles if u dont feel the burn) bottle filled with dirt.
in standing position hold the stick infront with your hands straight forward. twist the stick forward/backwards to pick up the bottle. when the bottle reached the top do reversal.