If you haven't tried coconut oil in your hair, you should! It's easy, cheap, and amazing for your hair. I buy the really cheap coconut oil that is not technically that great for eating, (it's extracted and processed differently) but it is still the same oil and has the same properties. The reason why coconut oil is so good for your hair has to do with its molecules being able to be easily absorbed by your hair.
The easiest way to do this is to not melt the oil, but rather work with it in your hands and work it through your hair as it melts. I've tried melting it and then applying it before and that was way messy.
Simply brush through your hair so it's smooth and ready. Part it or do whatever you need to so that you can work with about an inch of hair at a time. Take about a teaspoon (dime size-ish) of the solid oil and work it in your hands to start it melting, then work it through your section of hair, adjust amount of oil for hair section as needed and repeat with all of your hair.
You can comb through your hair with a wide comb to better spread it. Then put your hair in a bun and put on a shower cap or some saran wrap to hold heat in and help the oil penetrate better. If you want to use your blow dryer to add a bit more heat you can do that and leave it in for a shorter period of time (approximately 15 minutes) or you can just go about what you were doing and leave it in for longer (about 30 minutes).
To wash it out start working your shampoo in before you get wet. This will help with removing the oil, the oil will repel water if you start with water. Most shampoos have emulsifiers in them which will help remove the oil. You may also need to shampoo twice.
Enjoy your healthy, smooth hair!