You are using a chili sauce you purchased to create a powdered chili sauce? If so, why? Why not just use it in sauce form?
If it is a chili sauce you make from scratch, you might use your silicon sheet idea, but do it in a microwave oven. Do it a few minutes at a time to avoid burning it.
I have to ask though, why not just make a blend of dehydrated chili peppers and spices to create your chili powder?
Buy a variety of dried chili peppers, or fresh ones and dry them in the oven until crisp. Here is a recipe that details the technique for both methods. http://www.pickyourown.org/chilipowder.php.