My instinct is that it would be most appropriate as a soil amendment for soemone who is growing outdoors in an area that is very sandy, because that is when you need your medium to hold moisture the most.
Indoors, I would probably avoid it just for that reason. I have seen a thousand pictures of plants indoors dying of overwatering, and only a handful from too little moisture! It is easier to add moisture than to take it away.

If cotton compost and cow poop are your whole medium, you should DEFINITELY add a lot of lightener at teh very least- I don't know how good that combo would be by itself and would be super careful. But as amendments to sandy ground, oh hell yeah!