Hair Treatment for Curly Girls

Hi! I need advice on hair treatments (I prefer DIY due to budget range)

My hair type is around 2B–2C),I have thick hair strands but medyo low density. I’m not aiming for super pin-straight hair, I just want something like 70% straight after washing, so it looks smoother and more manageable without styling.

I’ve done hair botox before (last one was 2 years ago), and now my hair is back to being wavy/frizzy again. I’ve been looking into cysteine treatments recently, but I’m not sure if it would give that “naturally straight but still with volume” look.

Has anyone tried DIY cysteine or similar at home?

Would really appreciate honest experiences (good or bad). Thank you! 💖