I'll have to try some mug rugs. I became obsessed with thrift store wool sweaters a few years ago when I was making mittens out of them. Some were already quite felted, probably why they were at the store in the first place. But some, oh my, some were gorgeous sweaters and it was SO hard to throw them into the washing machine.
For those who had trouble felting in the new energy efficient machines. Yes, it does help to have lots of water but what really felts them is agitation and temperature shock. WAsh in hot, rinse in cold, dry on hot. My washing machine is HE. And some sweaters, even pure wool, just take more than one go round of that brutal treatment.
If your washing machine doesn't get hot at all there must be something set up wrong with it or maybe you have an anti-scald valve affecting it? After all, you do sometimes need to do a hot wash.
If you try mittens as I did, the lint really bungs up your sewing machine. It's not great for your washer and dryer either. Yes, I did a lot of them.