Prep Time 4 minutes Processing Time 20 minutes -Mash the avocado in a bowl until it is free of lumps and add the mayonnaise to it. Mix well. -Apply this mixture to your hair and scalp. Focus on the tips of your hair. -Cover your hair with a shower cap and wait for 20 minutes. -Wash your hair with cool water and shampoo. Finish with conditioner. -Squeeze the excess water out of your hair using a towel. Let your hair air-dry.