A lot of people do that to save time. From what I have read, "smaller" proteins work better than larger ones for a lot of people (hydrolyzed kind in products vs using eggs, yogurt, etc).

Though I don't use it mixed with conditioner, this one would work well for this purpose - it's strong, but liquid so it blends easily with anything: Colorful Neutral Protein Filler.
3B curls
Medium texture
Normal elasticity
High porosity