You shouldn't diffuse until completely dry, or at least it is not recommended because there can be the infamous case of frizz. I love Devacurl products, but a lot of curlies who don't like it, for it has polyquats. Thus, polyquats can add to build-up which will potentially bring frizz when wet to dry. I would suggest either low-pooing or if that doesn't help rid of build-up, actually shampooing and finding products without polyquats.
High Porosity, Fine, Thin Density, Low Elasticity