Hi there! The curly girl method often takes some trial and error. While the method emphasizes avoiding sulfates and silicones, it doesn't discuss other ingredients that can react in your hair--specifically glycerin and protein.
Protein can help build up the hair is not BAD per se, but it is possible to overload on protein-- this will cause hair to be stiff, coarse and dry.
Glycerin is also not "bad" - what it does, is attract water molecules. When the air is dry as it tends to be in the winter months, it can actually pull water out of the hair, drying it out.
Many Deva products contain large amounts of these two ingredients. I'd recommend seeking out products without these ingredients and I think you'll be happy
it's a bit Of trial and error but you'll get there!