I haven't tried this myself, but I've been told that Mane n' Tail shampoo/conditioner is great for thickening up hair. It takes about a month to see results, but I've been told it works! And yes, this used to be for horses, but they reformulated it for humans
Well usually, a greasy/oily complexion is caused by your scalp overproducing oil in an effort to make up for the dryness. (Hope that makes sense). I personally don't cowash every day - I use a sulfate free shampoo every few days and a sulfate shampoo every few weeks to get rid of buildup. I don't have short hair, so I can't answer your pineapple question, but here's a thread that might help!
Several ways to look at this. Usually people use a cheap conditioner to cowash with, and then they use something more nutrient-rich and thick as a leave in/conditioner. Hope that helps, let me know if you have any more questions