The moment of truth in the golf swing is when the club impacts the ball and using an impact bag will help you get the correct feeling of impact
Although not a very pretty shot if you level your shoulders to the slope, aim left and walk through the shot it can be very effective
Stop thinking about how far back to take the putter or how hard to swing, your mind can do that automatically, and you can prove this by practicing your long putts by just looking at the hole and stroking the putt without looking down at the ball