If you mount a magnet, I recommend that you do it in a way that makes the magnet easy to clean.
An idea that comes to mind is to epoxy the magnet to the end of a section of fiberglass rod (arrow shaft), pass the rod through a hole in a PVC pipe cap and put the cap onto a section of pipe large enough to allow the magnet to slide up and down the pipe. Make the pipe long enough to hold in your hand with 1/2 the pipe still exposed and cap the other end. When you grip the pipe and pull on the rod, the magnet will slide up the pipe and most of the junk stuck to the outside of the pipe will fall off, the rest will slide up the outside of the pipe until it reaches your hand and then as the magnet continues up the pipe, that junk will also fall off.
If you don't "demark" between the magnet and the junk, your magnet will quickly start to look like a sea urchin and will lose it's effectiveness... requiring you to pick the tiny filings off with your fingers. Messy and dangerous... sharp little rusty things in your skin... ouch!
GS