If you have brushes dedicated to just drybrushing, they get better with time.
Yes, they go frizzy, but with drybrushing, that is indeed a good thing, as you get a more \'feathered\' and soft blending.
I use a fairly large flat headed brush with horsehair. To the scale of the screen the size and cross-sectional shape of the tip is something like this: [[[[[[]]]]]]
That way it can be used on large things like tanks aswell as a rough shade on smaller minis.
If you intend to use it on skeletons, the only consideration is to finish drybrushing all the bone before you begin working with any other colour.
I\'d recomend spraying skeletons with black primer; then painting the whole thing a dull dark drown; then drydrushing liberally a few coats of a dull meduim brown with a larger flat headed brush, and finally drybrushing to taste with a bleached bone colour and a smaller flat headed brush to complete the drybrushing stage.
I would then water down some of the bleached bone adding just a touch of the dull medium brown, and gently wet-shading with that just to neaten up any areas you arent quite satisfied with.