One hint when grabbing 'the real thing' concerning dirt. Be sure to get fine sand, instead of normal. It should be - I reckon - the size of dust. If you use sand that is more rough in texture, it will seem that your AT-ST is walking through a cobblestone desert.
I get my sand from playgrounds (don't tell to anyone, it's just a handfull). Worked okay on my BMW Motorcycle pausing in the Nevada deserts.
More pictures on my website; click link below.