Good putting starts with confidence. Bad putting starts with a lack of confidence.
If you have to play a golf course that has really slow and bumpy greens, I feel for you. Whether it is the result of poor conditioning (or maybe the greens have been aerated), it can wreak havoc with your putting confidence if you take it too seriously.
Putting is much more of a mental endeavor than the rest of golf is. On the green is where the strokes really matter. Instead of having an entire fairawy or green to hit, you only have a 4.25 inch hole. Anything that doesn't go in is a failure.
Putting confidence is very fragile. It can literally be broken with a single missed putt. Before long you are trying weird looking grips and crazy putter heads trying to find confidence in something.
In the end, confidence in yourself to be able to make a putt is what really counts. It doesn't matter what implement you use, or how you use it. If you believe you will make it, you probably will. If you believe you will miss it, you probably will.
Don't risk your confidence by trying to play a serious round of golf on a course with slow and bumpy greens. You are far better off to just step up to the putt and go through the motions. You can blame the green and the lack of effort on the putt, but not yourself or your stroke.
And NEVER try to practice on bad greens. It is pointless when you realize the best you can hope to do is no harm.
Remember, confidence in your putting is far more important than anything else you may use to get the ball into the hole. It is not worth risking the quality of your putting because of the lack of quality of the greens.
Now let me show you the right way to putt.