Here is a link to a video that shows how to use powdered sugar to dust a colony for varroa mite control.

Some equipment needed

Powdered Sugar, 3/4 cup per medium super, 1 cup per deep super
Window screen or flour shifter
Measuring cup
Brush
Usual hive inspection equipment

NOTES:

Colony must be on a screened bottom board

Current technique is to not break colonies apart but apply appropriate amount of sugar through top super

Notice in video that I forgot to brush sugar off the frame top bars. You need to get the sugar down between the frames!