Once I finished weaving the ends, I set about felting. Yesterday, I purchased a 5 gallon bucket, a plunger, and a package of tennis balls. I filled the bucket about halfway full of hot water, threw in the tennis balls, the mittens, and some Woolite, then used the plunger to agitate. It took about an hour, but I think they turned out really well.
Now to get some Lionbrand Wool-ease to do the cuffs (so the cuffs do not felt when my brother washes the mittens).