Creating roughened edges with variation with the brush tool

Hi there,

I'm trying to recreate the style of some illustrations and want to achieve the same kind of edges on my brush stroke as in the attached screens. I can see from the way and speed these were done that it is not done manually so to say, but just generated.

I've tried by setting an accurate fidelity and higher variation in the roundness but it doesn't really do the trick - does anybody have an idea of how this could be achieved in a smart way?

Thanks a lot,