My daughter has this issue, super wavy hair underneath a layer of straight hair on top. She is only 5 though so I don't do anything to encourage the top to be wavy and just let it be.
You could try using those curl tubes from Sallys, I forget what they're called, but they're no heat curlers. You put your hair in the tube and it curls it. Maybe if you sleep in them when you wake up in the morning your straight layer will match the rest of your hair? Just a hairspray and go kind of thing? The only other way I know to encourage curl is scrunching or try blending your straight layer with clumps of curly layers and twirling them together to encourage the curls. Sometimes there's just nothing you can do though, like my daughter she's got the top straight layer that makes her hair look straight, but then you pick up that layer and there's all these waves underneath.
2(I have no idea what pattern), low porosity, mix of medium and coarse, dense
*Have just discovered the amazingness that is the "Spritz and Condish" routine*
Shampoo: SM Moisture Retention Shampoo
: VO5 Vanilla Mint Tea Clarifying Conditioner
: GVP CB, Garnier Triple Nutrition
: Whatever conditioner I used + EVOO or Argon oil
: Organix Moroccan Curling Perfection Defining Creme, EcoStyler Gel (krystal)