How can I keep African American hair straight!! please read description!!?

i am african american also and i have a perm my hair is to my shoulders what i do is wash my hair comb it out gently while wet then i blow dry it. after it is dry i part my hair into tiny sections and go through it with a one inch gold n hot flat iron and it works fine.to get my hair growing i take skin hair and nail vitamins which really do work and fish oil helps to put natural oils in your hair so you don't have to use grease and oil which causes our hair to be stiff and lifeless. hope i helped by the way the flat iron i use costs about thirty bucks. btw tinier flat iron equals straighter hair.