Fullers Earth (aka Bentonite) is a good way to achieve a dusty look either on costumes or on set pieces / props. Cat Litter provides a larger-clumped equivalent. Both are made from absorbent clay but can become slippery in large quantities.
There are reports of problems with singers / actors (and audience) inhaling the dust (it’s a lung and eye irritant) so this effect should not be widespread, or used to create a dusty atmosphere – it’s only for localised small effects.
Flour, corn starch, sugar or other organic products should NOT be used on stage as they are highly combustible in dust-form.
Real feathers can bring on allergies in asthma sufferers. Synthetic or fake feathers are a suitable replacement but care should be taken as they are most likely flammable.
Food – Pies
MessySupplies sells a range of pie and slosh products (in a range of colours)
Mud effects on scenery can be created using products such as Flints Mud.
Rubber Crumb could be used, along with foam chips / offcuts dipped in paint then squeezed out. The foam will need to be treated with flame retardant.
Polystyrene / Styrofoam can be used in chunks, which can then be coated with Rosco Foamcoat (to provide a hard-wearing flame retardant surface)
More information coming soon!