Learning how to judge the speed of a putt is a developed skill which can be improved with a simple drill like this one
Position a spiky ball under your armpit and oscillate your arm, allowing the muscles surrounding your shoulder blade to loosen and fire in the correct manner
Many players release incorrectly because they can not physically produce the internal rotation of the hip needed in the downswing and release, use this quick half minute stretch before playing to work on your hip flexibility and allow your body to make the proper swing