The good news about making textured painting is that you don't need to draw perfectly. As you can see in the following picture, the texture of the painting isn't perfect:
About textured techniques, I found this video very useful. Even though it is in Spanish, you can easily learn about textured painting step by step. You may need to look for the right materials on the interntet, but everything else is shown on the video.
Also, I found this video well done. The music, the author's logo, the transition between each step and the performance of the zoom in and out helped to reach the purpose of the video: teaching.