Grease Pencil as part of Blender is now a very powerful 2D Animation Suite of Tools. Very stable, with Automatic In-Betweening and Bone Rigging.
Characters can be animated completely with normal Blender Transformation Tools and an incredible "Sculpting" Engine.
Make sure you are using the latest "Blender Builder" release of version 2.78.1 found here:
https://builder.blender.org/download/
There are a growing number of Step-By-Step video tutorials demonstrating the most important Grease Pencil techniques found here (with an Optimized Grease Pencil UI):
https://www.youtube.com/channel/UC-t3I3gSAsZWsCvsxUkBZRA
The latest frame-by-frame with Interpolation video is found here:
Enjoy these and learn a lot.
Greg Smith
Grease Pencil is marvelous in making an advancing Walk a relatively simple thing - streamlining the introduction of variation:
https://www.youtube.com/watch?v=Q2iyTMOkcdQ
Let's uncover these mysteries,
Greg Smith
In this video, we examine and construct the advancing walk cycle of the TWO-Legged Man - unlocking more of the Mysteries of Blender's Grease Pencil Suite of 2D animation tools:
Mystery of the TWO-Legged Man
I hope you enjoy and learn from this,
Greg Smith