I managed to get through the oil wash stages on my tactical troops from the Calth box.  This was a bit of a test, and I'm pretty happy with the results.  To review, first was laying down some basic highlights with the airbrush (blues), adding silver, gold and black (plus some grey and red details), then spraying with future floor polish before adding an oil based black wash.

The idea is this... future floor polish is an acrylic gloss finish.  This will protect the paints underneath from the oils and allow me to rub off some of the black after its partially dry.  The gloss finish allows the paints to flow nicely, and since its from a bottle I can airbrush it on.  The oil wash is just a mix of thinner and artist oil paints.  I'll be using black, but you could use whatever makes sense for the colours your are shading.

Tactical squad with the acrylic gloss coat

Closer look at the gloss finish 

All ready for the oil wash

Oil wash applied

Ok to dry for a few hours