I've heard about making a 'wash' with pastel powders, but have never done it. I think that is what you are refering to.
I use the 'dry' method. Normally here's a few things I've found:
- the paint usually has to be 'flat'. The powder won't stick very well to gloss or a gloss clear-coat.
- I've had trouble getting the powder to 'stick' as much as I wanted and found that sometimes you have to rub it in a bit with your finger.
-you'll always have extra to 'blow' away, but that's the idea. Assess what it looks like after the loose stuff is gone, and then reapply until il looks like you want.
- A clear coat will diminish the effect of the pastels a bit.
M.