As I have said many times before, 99 % of the success of turning the hands comes from the proper sewing of the fingers. If the hand is properly sewn, then the fingers turn easily.

Use this template as your guide.  Make some practice arms and work with them.

Keep in mind that the thickness of the fabric, the give of the fabric and the seam construction all play a part in the turning. 

The Finger openings should be straight across.  The openings mus be large enough to accommodate the finger when pulled through.

The Tip of the fingers must be smaller than the opening.

Sewing to the line where the top of the finger is drawn is crucial for a well formed finger.

The opening has to be large enough to pull the finger through

Sew down the arm to the little finger. Stop.

Turn the fabric. Sew across on the drawn

line. Turn the fabric sew up the next finger

and stop at the drawn line that forms the closing of finger one.

Sew down the next finger, stop

at the tip. sew across, making sure that the tip is smaller than the opening you are creating.

do this with each finger until you have all sewn in.

Fingers take practice.  Even the most skilled doll maker  has finger problems at times.  The key is to think of the finger as just another part of the doll.

When trimming the finger to turn, be sure that the finger is trimmed close to the lines.  Know your fabric.  Know if it accommodates the finger size you are trying to create.