Tankwa dust is alkaline. When mixed with regular water and car shampoo, it can harden and stick to plastic surfaces.
To remove it, use a vinegar solution (1 part vinegar to 4 parts water). Wipe down plastic panels, the kitchen area, and floors inside the vehicle with this mixture.
For the exterior, you can wash off the dust at self-service car washes in
Ceres on your way back.