I used acyrlic paints mixed to a very watery wash, layered it on step by step, using various shades of gray, black and oranges { rust colour }, I let each layer dry and washed the whole tank again. I now know to 'feather' the wash edges with a wet paper towel. The mud is dirt from my garden, white pva glue and lots of brown acyrlic and then dabbed on using a wet paper towl and old brush, I let the main tank dry and worked on washes of rust colour on the tracks{ these I had taken off to paint }.