I paint most engine details with a fine brush and a magnifier,aided by a good slice of patience and frequent cups of tea.
Some parts like fluid reservoirs,exhaust pipes,or ignition harnesses (sometimes) can be added later but generally there is no easy way.
I dirty everything up with a nice oily wash once I'm happy.
I'm not sure if you are doing a Bf109 (with a mostly black,inverted V-12,liquid cooled,Daimler Benz engine) or a Fw190 (with a mostly aluminium,radial,air cooled,BMW engine) but the same principles apply. There are plenty of online images of both and if you are stuck for any detail I will probably be able to help you out.
Cheers
Steve