Sweet looking gestures sketches from life! That's definitely a good practice to build up one's skills. I recommend Jazz that you check out Stephen Silver's blog, particularly episode 6 of his podcast where he describes his method of "memory sketching". It's both fascinating and inspiring to listen to. Podcast link in his homepage, left column.
The green haired painting child (?) above looks like it was done with pastels on pastel paper. Have you tried that medium?