hey..I had good results with a pinion gear(the small gear off the shaft of a motor) ..a 10 or 12 tooth I think..I used model putty..apply thin ..then use the pinion gear with a paper clip as an axle in the hole so you can roll it up and down ...clean gear often and youll get good results..
take a look here..i used it on my Tamiya Porsche Turret King Tiger..
http://www.rcuniverse.com/forum/m_49...tm.htm#4986780
also ..dont know why ..but the Red color you see is really brown in real life..comes out that way in digital pics for some reason