The overflow hole on our bathtub was smelling really bad. I used a few methods to clean it. Doing so, I lost a brush deep down the overflow hole, probably 12" deep. The brush is pretty much a long metal wire with plastic bristles coming out of the last couple inches of it to form a pipe cleaning brush. It's actually used for baritone band horns. There's nothing on the brush for me to hook on to from the top. Pushing it out from the bottom, through the drain, seems near impossible as well. Can anyone help?

two options..
keep trying to hook something on it to get it out.
open up the wall behind the tub to access the overflow assembly, take it apart and remove the brush. (of course if the tub is on the first floor and you have a basement below you can work from their)..

A strong metal magnet might retrieve it. One of those 3 prong spring loaded griper tools would likely get it. They can usually be found in auto parts stores for just a few dollars.