I prefer Japanese style, nice long & rigid (nylon?) bristles -- good for cleaning up and along the cantilever, and also the front yoke / pole piece. The front pole piece can be hard to access on a Koetsu, but it's even more important to keep that clean than the gold cover because it will attract magnetic dust (really, really bad - catalyst for chemical reactions). Carbon fiber bristles are far too soft and compliant to knock off the really insidious crap.
These kinds of brushes are included on various Japanese products -- Shelter cartridges and Fidelity Research cartridge carriers, in my case. I hear they may also come with Denon cartridges. To clean up a cantilever & yoke I only use a very small section of several bristles, parted from the main body of bristles. Use my 2nd hand to brace holding hand for steadiness.
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