If you want wavy hair from curly hair, then use good products for the curly hair. If you have straight hair, then use a thick fat curling iron to get the waves for your hair. They give a grungy feel to the hair not so finished.
In the 80’s it was the practice to turn over the head to achieve the look of wavy hair. Don’t do it as t will give the wrong look. Use a quality diffuser for wavy hair. Just use a little and don’t rub it in too much else, you will end up with frizzy hair. This means hands should be minimally used while putting in the diffuser.
