Start with a deciding which type of soil or look you want to achieve. I know `red dirt`is common down under so a red oxide primer is a good start.
Follow with a Red - Brown wash. Then dry brush the tops a lighter color for contrast. Now add any vegetation or grass on top of the soil & rock. Add larger elements after the lower ground work is complete.
Basically its the same sequence as planting a garden. Get the soil & dirt looking right before transplanting on top of it, larger items take longer & more effort so they would naturally come later.
The same sequence was done for this lill`scene in 1-144 scale. The only difference is tones of gray were used instead of reds. Shrubs & grass are easier in smaller scales, here model RR scenic ground work was used.