i've got insanely thick hair as well and what i do to make it not crazy is wash it less often. i find that if i wash it with shampoo more than 2 times a week it gets all HUGE and fluffy and i feel like i'm in a motley crue video. i still shower, and i'll condition my ends (they are like straw, of course) but shampoo is seldom used since it does feel like my hair is stripped.
so, what i do in between is spritz my hair with rose water/witch hazel/lavender EO.. it helps to reduce the oily look, and makes it smell nicer than most shampoos.
also, i basically treat my hair like it is curly.. i know that curly girls are not supposed to brush their hair- just comb it out after a shower and leave it alone. i do that now too. once i stopped dry-brushing my hair, it was alot um... flatter.. even after shampooing the hell out of it.