Which method do you guys like to use? Brush or Spray and when is the best time to wash? If you wait till the model is completely finished then when you blot and wipe up the excess you will destroy all of the photo etch stuff. What do you guys recommend?

Washes
An airbrush would not be a good tool for this. As mentioned in the link above, I don't subscribe to the blotting method and having a lot of fiddly bits at risk of being dislodged is yet another reason.