Do you use a leave in conditioner? Try using some (pea size, maybe more for your long, thick hair) of your rinse out as a leave in. Since your roots tend to get flat/greasy, I'd only add it from ear level down.
I see in the other thread that you are looking for a hair twin. Check this thread.
Share your Hair Biography
For good product recommendations and help, you should know at least some of your hair's properties. There are some links to help you figure them out in the hair bio thread. Also check livecurlylivefree.com. They have a service that tells you texure, porosity, and elasticity. Here are some other links.
determining porosity and elasticity help?
The Wavy Tales: How to classify your wavy hair
Porosity and Curly Hair | NaturallyCurly.com
(a blog to help new wavies, go to the how do I get started page)
2a (nc.com) 2bFi (Fia), very fine, thin, low/normal elasticity, porous, CG, doesn't get weighed down
Cowash: Tresemme naturals
Rinse out/leave in: Renpure Organics (red)
Curl enhancer: FSG
Gel: BRHG, Salon care aloe, Ecostyler Krystal (normal dews)
PT: ION effective care, IAgirl's gelatin PT
Low Poo: renpure (red), Ion swimmers