There's quite a lot of scruffy ground on Selly Oak. My normal method of reproducing this involves lots of Wilco "Nutmeg Spice" emulsion, but I wanted to up my game this time, so added "Chocolate dream" and "Earthy Hue" to the palette.
Mixing the three on the model gives a much better effect - but still too smooth.
Not to worry, sifting some fine sawdust into the paint does the job. The stuff doesn't sink in, you have to work it with a stiff paintbrush.
I know there are "proper" modelling paints for this sort of job, but they cost a fortune for the amount I'd needs, and I'm not convinced they are that much better. Maybe if you build a 1/32nd scale tiny diorama, but for a layout where most of it will be covered with undergrowth, stick to the matchpots.