Tips for greasy hair anyone?

I am 19 yo. have naturally curly brown hair, mid-length, and it so far it hasn't been very problematic.. but recently, maybe due to hot weather and constant sweating it gets greasy very easily. Even when I wash it, I feel like i didn't wash it enough. I still can see some traces of dandruff.. i rub it with my fingers during the wash so i could clean it, but it seems it is making it worse. The problem is also, it's curly only at the ends.. and it gets tangled, so i have to use conditioner, but the conditioner makes the rest of my hair even greasier! What can I use, or do? How to wash it properly?