The engines are nothing fancy. This is how I paint radials. The crankshaft is painted gray first and allowed to dry, followed by the cylinder heads with black. I then, if needed paint the details on the crankshaft. Once all is dry, I use silver and drybrush the cylinder heads and the bolts/ring on the crankshaft and any other raised detail. If I accidently put too much silver on, I'll go back and dry brush a little black to tone down the silver. I'll then add them to the cowls. Then if I want the weathered look, I weather the engines inside their cowls, so I know where things leak and such.