Your hair has to be at least a 1/4 of a inch (a grain of rice) for the wax to adhere to your hair. If your hair is not that length you must wait 7-10 days to grow it out.
When you exfoliate it helps to remove dead skin cells, which gives better results for your wax. You can make a natural scrub with 1/2 cup sugar (white or brown) with enough extra virgin olive oil (or Grapeseed, Jojoba, or whatever your favorite may be) oil and some tea tree oil. Mix until it becomes a paste. With a circular motion gently massage the mixture into your skin. Then rinse well.
If your hair is more than a inch long (2 grains of rice) then you want to trim with scissors. If your hair is long or over grown this will cause discomfort during the brazilian wax.