>>6479867"for what purpose" is what comes to my mind, but then I did something like that in pic related to blend the oil post shading later, no pre-shading done in my tho as I prefer post-shading and I don't like much how pre-shading looks (each to his own and when well done it looks quite dramatic and eye catching). But rather than dry brushing it I painted it as carefully as I could and also apply it to raised details so they pop-off more later with all the weathering.
(album so you can see what I meant with post shading with oils
http://imgur.com/a/1UoMQ)
The thing is that it depends on the volumes of what are you're working on and what look you're going for so it doesn't look too cartoonish or weird, so try it as I can't image it in your project, and personal satisfaction is what really matters in the end
