So you want to dry wash. Say did you know if you cover the rifle tray with aluminum, Plexiglas or wood veneering after the first rifle. You will recover more of the fine gold during us. Not only will you recover more fine gold you will keep a lot of the dust from blowing back on you.
But, another good trick from keeping the dust off you is to just work up wind!!

.....I have a Keene 151 dry washer and it works great. Gets me real dirty to. It has a lot of power to blow off a lot of light material and in that light material may be some fine gold. My rifle tray has 3” sides on it. So I bent the sides of a piece of Aluminum to fit over those flared ends. It simply slide on over the tray leaving about a 3” space from the tray to the top of the cover. Just don’t cover the area that the material floes in from the hopper. Set up properly the material will blow back into the rifles on its way out the dry washer giving you a better chance of recovering the finer gold. If you have a puffer unit or a wooden unit, you may need to put in a spacer on the side of the tray itself to lift up the cover over the rifle allowing the material to move down and out easly. I would say at least 2” of space between the tray floor and the bottom of the new cover. That should allow good movement of your material to flow out smoothly.
I hope you guys like this trick..