When applying an overpspray tio simulate dust etc do you do this before washing and drybrushing or after? I also use pastels but do this at the very end.

I think the best way to go is finish all your washes and drybrushing first before spraying the dust layers! Spray thin light layers and try not to hide too much detail either. I use a light earth dust layer first on the running gear and then spray lightly over this and take it further up the model with buff. I actually give the whole model a slight overspary with this as it ties all colours together and also makes the overall finish more matt.

It may be a good idea to direct these questions in the painting forum rather in the armour section!

I have always thought the best way to approach painting anyhting is the to paint in the order it happens in real life. Primer, Base coat, shading,washes drybrushing and then apllication odf mud ,oil stains and anything else stuck to the vehicle. I believe this will give th emost realistic finish.

Josh Weingarten
Aka shiryon

I agree.....If you think about the way the real thing gets dirty, the dust would be the final layer.