I am a little lost - you want to elongate your curls to reduce shrinkage or get rid of frizz or make it more manageable so you can see your curl pattern?
I am not a huge fan of keratin because it is added things to deal with and I am a minimalist so I do as little as possible. But there are a lot of different brands, I think people have been successful with Coppolla. I wonder if the one you used was just too harsh? Or if you did not moisturize properly for example if you like to shampoo it should not be that frequent maybe once a week, make sure you are not using a shampoo with SLS, you would need to use a moisturizing DC maybe even with heat, since keratin is a protein stay away from other proteins.
For me I would need to understand your goals better.