I made the sandbags by rolling sculpting clay out into 1/8" diameter sticks, then squishing them a bit with my thumb and slicing them into sections about half again as long as they are wide. I then pinched the ends to create the "bag" shape and stacked them while they were still soft. After they had dried I painted them with a 50/50 mixture of wood glue and water to ensure they stayed stuck in place. I was going paint them but I think I like the color just as they are.
flocking 24 square feet of surface was a pain
but I think it turned out pretty well
I might add some sand to the craters, they look too tidy
an Airfix Mk I for size