Tamyia 'smoke' was used to make the effect of spilt oil on the Panzer IV.
I found a wealth of modelling ideas in the 'Flames of War' website and painting guide booklet. Even though the game is for 15mm figures, the supporting material and web site is handy for any scale. They are bringing out even more painting/modelling publications all the time. Their latest covers the German Whermacht, really useful stuff as I have always struggled to find detailed tank colour schemes.
I also used the spices to help camouflage the men. "Who threw that?!"