Various effects to tidy up:

• A dusting of the exhaust with Mig Productions “Standard Rust” pigment (P025), followed by fixing with application of Tamiya X20-A thinner.
• Application of the “Soot” Tamiya weathering powder to the end of the exhaust and adjoining fender. 
• “dry brushing” AK Interactive “Dark Steel” pigment (AK086) on the machine gun barrel and various metal tools. I must admit to liking this pigment – as advertised it is very fine in consistency and realistic looking.
• The wooden “blocks” stacked at the front of the tank were painted with Winsor and Newton “Burnt Umber” oil. A short while later it was substantially removed by a wiping a cotton wool bud across it, leaving a reasonable approximation of wood grain.

Reference

1. Wood grain painting guide (Wingnut Wings)