This might sound a little bit crazy but there was a segment on Access Hollywood about two years ago that showed how some Hollywood celebrities like Jennifer Aniston and MKA get their wavy hair. I've been trying to find in all over the web because wavy hair is something I've always tried to achieve but fail miserably at it time and time again.
From memory I think this is how it's done:
-Wash your hair and towel dry
-Spray some sort of curling product in your hair (any one that you own)
-Take some loofahs, cut each of them up into about 3 pieces
-Take a piece of loofah and wrap a section of your hair around it. When you get to your scalp, tie the loofah piece into a knot to let it rest on your head. Repeat this process about 8-10 times until you've wrapped up all your hair
-Let your hair air dry. When hair is about dry, put in some leave in conditioner and run your fingers through the strands to get the look you want.
-Hairspray
I haven't tried it yet and it sounds kinda funny but it's something to try if you've tried every different method possible and none of them have worked for you.