USE LOTS OF REFERENCES!!!! haha they help me a lot. also tutorials and speedpaints also help a lot too. they give you an idea on how to go about things. i think using the water tool is alright honestly as long and you blend nicely and evenly and use good colors while shading. also its just a good way to start off until you get better and develop your own way of doing things. so yeah. just. References. Tutorials. Speedpaints. Practice. Patience. and experimenting with different tools/techniques should help.