I think most who use oils only shade and highlight, over a base of the common enamal colors. What I like to do is mix my oils a shade darker or lighter than I need then spike it with some of the base color I'm working with. This not only aids color uniformity, it also helps it to dry quicker. Here are a couple of my kits, so painted.
You'll notice the multi hue camo each spot was shaded & highlighted with oils,NEVER again.
This is my 1/8th scale Micheal Wittman, black is it's own little problem by no means a straight foward approach. The S.S sapper is in 1/9th scale, both are sculpted molded cast and painted by yours truly.
The devil is in the details...and somtimes he's in my sock drawer. On the bench.
Airfix 1/24 bf109E scratch conv to 109 G14AS
MPC1/24 ju87B conv to 87G Rev 1/48 B17G toF
Trump 1/32 f4u-1D and staying a1D Scratch 1/16 TigerII.