I can only tell you the results of my experiments with the same issue...you can decide for yourself if you want to go through with this procedure....it worked for me.
take the beater and soak it overnight completely submerged in water with a few tablespoons of chlorine bleach. The next day dump the water and use plain old fresh water on a stove and boil the beater for a good twenty minutes. Let it sit around for a couple of hours or days to dry out then.....take a piece of scrap wood and drive some skinny little finish nails through the wood letting them stick out the other side as far as you can up to about a half an inch...now use this tool you just fashioned to stab into the ball all around so that it sort of separates the fibers and fluffs the thing up a bit just like a piano tuner does to piano hammers to set the action just right. ( you can also use a darning needle held with a pair of vice grips) Then when you get the ball in the desired shape, remembering that felt is actually just wool you can also take a piece of 80 grit sandpaper and sand off all the remaining fuzz and funkyness. The chlorine is just to kill mold and remove basement odors and such, don't expect it to turn white again, however the feel of the beater will be good as new or better when you are done.Good Luck. Have fun.
Glen