SMG Basing

I am finally getting around to the Soviet SMG bases. My son has two platoons so I am basing each platoon a little different. One platoon I decided to go with a sandy base.I put on the plaster then sprinkled sand on top. Big mistake. As I am painting the base the sand keeps coming off and into the brush. Miserable!

The other platoon I am basing the same style I have been doing.