This is a novel way to ease key bushings.
The standard way is to iron them or compress them. This way actually shaves them.

A key may bind on the balance rail pin or the felt bushings.

I use a standard large set of tweezers. They need to be the right size.

To ease the balance rail hole, I just insert the tweezers end into the hole. Be careful; not too much.

To ease the felt bushings, I insert the tweezers and move them back and forth.

I’ve always done this and never really understood why it worked so well. I thought I was just compressing the felt.

Then one day, I looked at the tweezers.

I found powdered felt. I realized the tweezers were shaving the felt! No wonder it worked so well!