The acrylics should be fine under the artist oils. It's really only enamels you have to watch out for, and even then it's not a big deal if you use a gentle thinner for the oil wash.
As for drybrushing, I prefer to do it before any washes (I use Model Master enamel Dunkelgrau for most of my drybrushing and have found it works well across various interior greens and the RLM 66 of late Luftwaffe birds...stuff like the green-blue of Soviet jets requires a different approach though).
On the Bench: 1/32 Trumpeter P-47 | 1/32 Hasegawa Bf 109G | 1/144 Eduard MiG-21MF x2
On Deck: 1/350 HMS Dreadnought
Blog/Completed Builds: doogsmodels.com