Fingertip release

My coach told me that my index and my middle finger should be pointing at the rim when I shoot. It's pretty effective, but sometimes I tend to only use my index finger to release, hence only my index finger points at the rim.

How should I release the ball (fingertips)? Should I just "feel" the rhythm or is there a proper way?

Bonus question:
Perfect practice makes perfect.
Not everyone has a perfect shot.
How exactly can I improve my jumpers if they aren't really that good yet (tho im not sure if its good or not)?


Thanks.