I got the original brush-off inspiration when I first started 3D printing now years ago. I am certainly not the first person to think of the idea. I have seen it mentioned by other 3D print people when I was reviewing Amazon user-reviews when picking this new brush. Yep the brush-off is a real brush. A small wire brush to be exact.
It is used to clean the old hot plastic debris off the nozzle of the FDM printer. It works best when the nozzle is up to full temperature.
I use the brush to clear the bit of ooze just before printing starts. The plastic cools immediately in the brush and the user must pick it out and keep the wire bristles clean of the debris. Otherwise, it will melt back onto the hot nozzle. Yuck.
I can print literally for months on the same nozzle by keeping it clean. Neither nozzle brushing nor clearing the brush is a hard task.
My original brush was one I used in my machine shop for cleaning chips from threads (after cutting them) and other metal shop tasks. The handle was wood and a bit grimy. I think it dropped into the waste can, as one day it simply disappeared from my 3D printing area.
These brushes are also made with brass bristles. My wife likes to use them around the needle area of her quilting sewing machines to clear lint fuzz.
I highly recommend this or any similar brush be used to keep FDM printing nozzles in top (clean) condition. You might find one or two more useful around the workshop as well as the sewing machine.