I decided to do a variation on what I've seen on the internet and at conventions. I've seen people take sealant and either put it on felt or just right out of the tube. I never liked how either of these worked. The whole point of getting paintable caulk is to paint it.
I used DAP indoor/outdoor paintable (has to say paintable) sealant in Cedar Tan color and a caulk gun to squeeze out several lines on some wax paper and then used my finger to spread them out. I wanted the edges ragged, but wanted fairly uniform widths so I drew out lines on the reverse of the paper 2" wide.
After they dried, I dry brushed them using the same colors I use on my miniatures bases.
They turned out okay, but next round I'll put wheel ruts and some sand in for texture while the goop is wet. I'll do some curves and T intersections also.