this is my way
I first make every levelling in my dio with foam board. this keeps your dio very light. next thing I do is cover everything up with wallspackle. while the spackle is still wet I lay a piece of kitchen foil (the transparent type) and push my tank or whatever vehicle I use onto it to make the tracks. What I also do while the paint is still wet is pouring the first layer of fine sand on it. and let this dry for a day.
then I make a 50/50 mixture water white glue and go for the second layer of sand. this is also allowed to dry for a couple of hours. then again a 50/50 mixture of diluted white glue
and put that on the places where I want grass sprinkle the static grass on it and I let it dry for a couple of hours.
then I grab my AB and give the whole thing a coat of very dark brown. let it dry. in the next couple of stages there will be several colours sprayed on top of it varying from different types of brown till greys and different greens just till I`m satisfied.
then put in the long grass made out of a big softhaired brush that I bought at the discount departement of my local DIY shop. drill a couple of holes in your dio and simply put them in
(you could give the whole brush a AB-job first to colour it or you can just let it be his own colour - I`m talking about the blank haired brushes here- to simulate dry grass)
then comes the drybrushing with almost all lighter colours and that`s it
my two cents