steel wool and foam to plug holes to prevent mice

Actually, mice will "eat" through the brass or steel wool. I believe they actually tear it up and pull it out. Tried that trick once and still had the buggers getting to a spot I didn't want them. Found the remains of the steel wool all around it.

Tried foam once, but they just burrowed through.

The one item that kept them from doing anything was plain old LIQUID NAILS.
They quit coming in after I filled the hole with that. Never had any mice through any hole that's been filled with Liquid Nails.