This remains one of my favorite models. Your build up looks very good so far. Did you build two, or decide to swap out the smoke candles for a Jerry can rack? The Jerry can racks add a nice, personalized touch.
I respectfully suggest painting the 20mm and MG something closer to gunmetal. I also suggest painting the jack black, field gray, or the base color of the vehicle. This walkaround of the Sd.Kfz. 222 in the Littlefield Tank Collection that may offer some insight for adding a splash of color here and there:
http://www.ipmssantarosa.org/feature_walk/walk_017_sdkfz_222/walk_017_sdkfz_222.htmCare must be taken when using a restoration as a reference, but I think this one offers great insight on the Sd.Kfz. 222.
Good luck with your project!
-Doug