RogueM3- I'd go with the Conditioning Brush rather than the spur (assuming you're using foam pads). Dunno how it'll hold up, you can get it and fill us in
I use a stiff toothbrush-style brush and it works fine (and it's getting a lot of use as I continue to work on *my* M3
). I've been using the same one (forget where I got it, probably in one of those steel/brass/plastic bristle three-packs) for years and it's holding up fine but then I don't do all *that* much polishing.
A toothbrush, even a very stiff one, will have bristles that're too densely packed IMO. I want some space between them so the polish/etc. has somewhere to go. and yeah, you want mighty stiff bristles too.