Dusting is a technique of searching and trimming throughout your hair in order to rid it of damaged ends. Dusting damaged hair works best when you have areas of hair that are damaged because it allows you to retain your length as your hair grows to blend into your healthier hair. If you have areas of damaged hair this is a good way to keep your length while babying damaged sections.
I usually braid my hair up into sections and go through each section looking for damaged ends, this technique allows me to search through my hair more thoroughly and to follow up within the week with any braids I haven't been able to dust.
I have a section right at the front of my hair line that always has a lot of split ends, instead of cutting the hair I simply search and destroy by dusting the ends. This technique helps to lessen any frustration I may experience with knotting and splitting. A great way to follow up after dusting is by sealing your hair especially your ends with your favourite hair oil. The more you dust your ends the better you will become at it, dusting takes time but helps to retain length as your hair grows.