You could try the Cocoa Keratin smoothing treatment, it's much gentler on hair and it lasts for 5 months. Plus it comes with its own pre and post shampoo and conditioner to keep hair healthy.
For straighteners I use a Karmin G3 salon pro styling iron and it's really great for curly and poofy hair because it has ceramic and tourmaline plates and a heat setting that goes up to 460°F (very hot and very fast). You need a good heat protectant too. (Karmin also has a really great blow dryer, but I haven't bought it yet)
Keep heat exposure to a minimum and use a good conditioning treatment to keep frizz down. Also use satin pillow cases, cuts down on frizz and breakage. Oh and let your hair grow long, the weight will loosen the curls.