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Look at post #38 If your handy you could make you're own shave brush

I don't recall mine needing to be broken in. It's not one of my favorite brushes (to floppy maybe I should have set the knot lower) so mine doesn't get much face time. Very soft, brush though.

PCwoodcraft has horse hair knots, just one size, 24mm
I have bought several, they have a funky smell for about the first week but work well.