I am stuck on a problem. I have 54mm dioramas of Custer and the 7th cavalry fighting & I have been trying to make dust in the air. Any suggestions would be welcome

Teased out cotton wool or nylon fibre sprayed a dust colour.

Simply ........Don't try.
Concentrate on painting and creating a dust on and around the figures and horses.
Plenty of weathering powders available or mix your own from ground pastel dust.
Get the 'look' right and the viewers imagination will fill the air space with dust.

Maybe build a shadow box. You might achieve the dust effect by misting a light dust glaze on a mirror and reflecting the figs back to the viewer. Hope that makes sense.. Here's a link to BoxDioramas.com

http://www.boxdioramas.com/eckmann
Gary

Don't agree with that whacky old priest but he's spot on here

Grind hard pastel to dust
Each time you show the diorama, pour the dust on top