When combing buttercream, ensure that your buttercream is at the right consistency - not too stiff or too soft. Start by applying a generous amount of buttercream to the sides of the cake using an offset spatula. Then, hold the cake comb at an angle against the frosted side of the cake and gently scrape it along to create textured patterns or smooth finishes, depending on your preference. Repeat this process until you have combed all around the sides of the cake for a professional look.