2.6ouncesof maltodextrin for every 1/2 cup of butter in your frosting. If you have other fat in your frosting recipesuch as cream or milk, you'll need to add additional maltodextrin to keep a ratio of 40% maltodextrin to 60% fat in the end product. Don't want to do the math? You can always just add a little bit at a time until it works.
Use a double boiler or a metal mixing bowl over a pot of boiling water to heat the frosting until it becomes a thick liquid. Stir regularly during this process.
Remove frosting from heat.
Using a spatula, mix in maltodextrin (I found that when I used an electric mixer, it made the powder too clumpy).
The frosting will magically turn into frosting dust.
Use on everything!
Notes
Frosting dust lasts about a week. However, you could freeze it to extend the life. If you are using a frosting that you would normally keep refrigerated, I would suggest refrigerating the frosting dust as well.