What scale?
For 28mm I tend to make a ball of putty, flatten it roughly disc-shaped, and then squash down the ends, leaving the tallest /thickest area to represent the knuckles.
Then I shape the area of the disc that want the fingers, and depress (Or for different poses actually cut through) lines to separate each digit.
The thumb I add last from a small sausage.
This is how I added the hands for the tank commander on my Baneblade kitbash ( http://www.coolminiornot.com/forums/viewthread.php?tid=28464&page=2 )