How to wash relaxed hair?

ellos x] well, im trying to start a new hair regimen that works well for me so i wont always have to depend on the salons. i relax my hair every 2 months but the problem is when i wash my hair it gets poofy even if it rains and my hair gets wet it gets Poofy!! ugh its soo annoying. i dnt know what to do bc i dnt have a blow dryer with the nozzle or the big dome kind so i usually let my hair air dry and its just terrible. am i suppose to use a serum? & will it work on wet hair thats air drying? How can i get it to be sleek & straight again after a wash without heat?