Well my hair is 90 percent natural. The only part of my hair that isn't natural is my bangs, and I have this cut. My hair stays straight. I wash it, blow dry it, and then flat iron it with a 1/2 inch flat iron so I can get the roots. My hair stays straight. Pin curling will help. I've had my hair like this for about 1 and half now and I think you'll do just fine.
but if you are worried about altering your natural curl pattern then I do not know what to tell you.
I would say, wash, or co wash hair, baggy with light oils (coconut, castor, or shea butter oil idk), then rinse or wash again, then air dry, blow dry, then flat iron. I say do this because when I baggy with oils, when I wash them out and air dry over night I think that my hair is dried out, but when I go to blow dry and flat iron my hair, my hair oils up on its own. The oils keep my hair straight once I apply heat. Then pin curl or roller set your hair if you don't want to keep adding heat.