Short, fine, slightly stiff bristles, compacted together...works best.
Long fibers are not desirable.
You want to gently scrape away dirt, in a way that there is a very slight soft plastic fiber pressure on the diamond stylus, but no real stressing of the stylus, cantilever and suspension assembly.
this one is more like a proper ideal.I would not use the wife’s make up brush, it can cause more problems than it can help create cures.
You want to be able to control and feel the pressure and cleaning you are attempting to give the stylus. Which will include the cantilever right at the stylus mounting point, to clean away the grunge that builds up around where the stylus meets the cantilever. Doing this requires a slight pressure be delivered, no more than a few grams, like 2 grams or so.
Doing this right requires being under control of fine motor movements of your given hand. First, to brace the hand doing the cleaning on the chassis of the turntable for example, palm up.... and then gently move the finger and thumb that are holding the brush.....moving slowly. Possibly holding the tonearm in place on the given arm rest, so it is stable and can't get away from being under perfect control (motion wise)
Millions of people do it all the time, so it’s not a big deal, it just requires practice and the right/correct/best brush.
With the brush shown the amount of feedback in 'feel', from the brush is about as good as it is going to get. And that feedback in the hand of what is going on at the stylus and brush interface, is important, so you can know what you are achieving.