Vijay Singh is a great swing to model because he has great freedom through his swing, allowing him to get a great hip and shoulder turn and unload on his downswing through to an extended finish position
For most arc putters the conventional putting grip is very much like a regular golf grip but with the thumbs pointing straight down, allowing your arms to be in a more normal golf position
Some heel shots are caused because at set up you are too close to the ball causing your arms to start inside your shoulders