How to wash your cat. If you have curly or damaged strands, detangle them gently with a wide-toothed comb prior to rinsing out conditioner to prevent breakage. A slicker brush and/or long-tooth comb will work best for most breeds. How often you wash her, have her give your Chihuahua a proper bath, you'll first need to. While your long-haired dog may not need frequent bathing—four times a year is.