Once you've got muscles modelled and hooked up, stretching and buldging, you'll want them to deform a skin.

It's important to know how the cgMeshDeformer Modifier works, so you can minimise any problems you might have, and I'll explain a few techniques I`ve come up with to solve deformation artifacts.

How the cgMesh Deformer Modifier Works

The deformation works by having an object, a sphere, mesh or muscle act as a deformer on a surface of some kind.
The deformation pushes radially out from the centre of an object, or cross section in the case of a cgMuscle. This is important to remember, because if the centre of your deformer passes to the outside of the surface you are deforming, the direction of deformation will flip.

You can see here what happens to the direction of the deformation when the centre of your deforming object crosses the surface. This can happen at the ends of muscles as they narrow in diameter and get closer to their end cross sections. The Ray deformer method doesnt have this problem, and is an alternative in cases where you get popping muscles.

To stop this happening, you can use the Ray Deformer method with cgMuscles, which never flips or pops direction, but is the slowest deformation method.

A techniqueI used on the dinosaur, was to use ray deformers on all muscles to get the shape of the skin buldging nicely in the default pose. Then I took a snapshot of the deformed mesh and used that as the starting point for using the faster 3D cgMuscle deformation method.
Doing this gives you a lot better chance of avoiding popping muscles during extreme character poses.

Skinning can sometimes ruin the shape of your characters elbows, knees and shoulders. To stop this squashing you can use deformers to sit inside your characters joints, (its a good way to get really sharp creases if you need to) I used a muscle linked to the leg bones on the dino, as you can see here.

Also, to stop popping muscles, you can add smaller muscles deeper inside your character. The order in which the muscles are calculated is from the top of the deformer list down, so by adding a muscle higher up on the list, eg,in the centre of a limb will push out the skin to hlp another muscle maintain its direction.

A couple of quick tips to keep in mind,

- always use named vertex selection sets to assign where your muscles will effect the skin. (this speeds things up as well as reducing other problems)

- the more your muscles are aligned with your mesh lines, the smoother the deformation will be at modest mesh resolutions, if you see artifacting in the deformed skin, add a cgsmooth to your muscles, and a meshsmooth or relax to your skin.