Boomer, already know about the guage, but it would of required editing that this build wasnt for,
Here's a close up of the Trumpy version. It looks like its a armour cover over the top of the guage
As for the mud and splatter?
Mud is just paint mixed with the artificial sand stuff. Applied with brush
Splatter, make desired paint colour mix with water to very thin level (or other thinner depending on paint I used acrylic) position model on old newspaper with plenty behind as well. Then getting an old toothbrush dip bristles in paint mix and drag a finger along the bristles so the spray goes towards to target. I found a distance 9-12 inches worked well