Here is the description of how I painted it.
Painting the Cannon
The first thing to do, is undercoat the whole thing black.
1. Mix Glorious Gold (VGC) with Bolt Gun Metal (GW) - about a 50/50 mix, maybe a touch more gold than gun metal
2. paint the whole barrel, but no other metal parts
3. Once dry I washed the whole barrell with Devlan Mub (GW), concentrating in the barrells "ridges".
4. Once this is dry I did several washes of Babab Black (GW) over the front of the barrell
1. I painted many thin layers of Flesh (Derivan) mixed with Gunstock Brown (Derivan) about a 50-50 mix. This included the wheels and as well as the Cannon Frame.
2. Once this was dry, I painted a few very THIN (Highly diluted) layers of the above mixture of Flesh and Gunstock Brown but I also added some Burnt Brown (Derivan) and thinned this down quite a bit.
4. A final wash of Burnt Brown (Dervian) with Chaos Black (GW) about 80-20 mix was washed into the recesses.
5. The edges were then highlighted with Flesh (Derivan)
1. Painted all the metal parts, except the barrell, with Bolt Gun Metal (GW)
2. Washed these metal parts with a watered down Chaos Black (GW)
3. Highlighted the metal parts with a mix of White (GW) mixed with Bolt Gun Metal (GW) 40-60 mix. I like this better than using Mitheral Sivler (or any other bright silver colour), as I wanted a highlight, but not one that was bright.
Hopefully all this made sense. As regards to finding the equivalent colours for the Derivan paints, you can use this Paint Comparison Chart.