Unfortunately there is only one speed to practice putting with. Not many can sink a 50 footer often so the object is of course to try to sink it but if not then leave yourself as close as you can for any second putt and that is on any green speed and most breaks.
In this case it is best to do a practice round setting it up for what you want to practice. Then when on the green take your first putt if it misses then hit it away from the hole and try another until you sink it or run out of hits. Then move on to the next hole and do the same.
In doing this take notes on the hole so you will learn the breaks from different positions, unless you have a great memory.
I use single hole mainly to check my club and ball distance averages on different courses