A World War II diorama doesn't seem complete without mud-splattered tanks. Long-lasting mud for model tanks is composed of paint and a gelatinous agent that helps it bond to the model's structure. The sticky agent can be any one of a number of different products, depending on the type of mud you want. Most such products are safe to use throughout your diorama: over ground, around buildings and on the soldiers themselves. The viscous mud is applied to the tanks using creative techniques that will give it a realistic look.
Pour a small amount of either gel into the plastic container, depending on what kind of mud you want. Gloss Super Heavy Gel and Realistic water have different consistencies, with Realistic Water being less viscous. It can be poured on the ground around the tank and allowed to flow around the tread to create puddles. The thicker Gloss Super Heavy Gel can be used to paint directly onto the tank or build hills to make tank tracks. The Gloss Medium Gel is the middle ground between watery mud and caking mud. A thin to medium consistency is best for making roads.
Add paint to the gel. More paint will make darker mud but it will also thin the mixture. Start with a small amount of paint and mix slowly. Add more as needed.
Lay out a dust sheet. Set your tanks onto the cloth. Dip the end of the paintbrush in the mud. Cover the brush with a little excess mud. Hold the brush a few inches away from the tanks. Flick the brush so that the mud splatters the tanks. Splatter the mud near the base of the tanks. This is where splattered mud would fall naturally if a tank were moving along a muddy road.
Build roads with the mud. Carve a shallow ditch for a road. Mix a batch of mud with a consistency that will allow it to flow through the ditch. Pour the mud into the ditch. Allow the mud to set. Do not let it dry completely. Use your tanks to make tracks in the mud while it is still sticky. The mud will stick to the tracks as they rotate, giving a realistic effect to the mud distribution.
Refer to pictures of muddied tanks. A visual will give you a good idea of how mud splatters and sticks to a tank as it moves in a certain direction.