I feel your pain... I'm not an artist either. I watched a lot of video's on YT on how to paint rocks, mountains, etc.
In the pic below I put on a heavy coat of grey. I let it dry a day and then I came back with white. But I dry brushed it on. In other words, dip your brush and wipe off and much paint as you and dab and stipple it on. After that dried I kept doing the same process with other colors like brown, red and black. With some of the colors I would also water them down and then try to dry brush. It would create a kind of runny blotchy pattern that I liked when it dried.
With your project, I would assume you would use reds, brown, tan and black to get the color you desire.
I would add some paint in small sections and then just step back and look at it to determine if I needed more. It comes down to whatever you like. And if you don't like it... paint over it. For paint, I used the Home Depot sample paints. I love them and always stop by the paint desk to see if they are selling and oops paint. The samples cost .50 for oops and $2 for new.
Good Luck!
Ron
