I'm working on my first face-up right now and I'm using Derwent watercolor pencils. They are doing a really nice job. They go on easily and stay on well. I've only done one "coat" of color and it is already pretty saturated. The best part, you can wipe away any mistakes with water, which is a blessing since using an eraser can lead to unfortunate results.
To put it simply, I currently borrowing these pencils from my dad, but I like them enough that I ordered my own. You can get 24 pencils for about 20 dollars on Amazon and you get a nice selection of colors. For $45, you can get the 36 pack.
I have not tried anything with my water color pencils, but from the tutorials I have found making sure to put sealant on before & between each layer is key.