If there is one Weight Painting addon I recommend, it would have to be Voxel Heat Diffuse Skinning. Voxel Heat is an automatic weighting algorithm similar to Blender’s native “Automatic Weights”.
However, unlike Automatic Weights, Voxel Heat never fails to produce a result (no more “Bone Heat Weighting failed” error, yay!). And in most cases the results from Voxel Heat are great.
This addon shines when weighting complex areas such as overlapping meshes (think clothing over body, props attached on the main mesh, etc.).
However, even Voxel Heat isn’t perfect. The same algorithm that is responsible for nicely weighting overlapping meshes, also creates a common problem: it tends to fuse together areas that need to be separate. For exampe, the mouth and fingers of humanoid characters often get skinned in an undesirable way.
So it is best to use this addon as a tool and not a magic wand. Understand it’s strengths and learn to work around its weaknesses and it will serve you well.
“Automatic Weights” generally works great in the areas where Voxel Heat fails and vice-versa. So the two complement each other beautifully. Throw a little manual weight painting into the mix and you have a powerful workflow capable of weighting any character with ease.
The video below demonstrates CGDive’s workflow. It demonstrates the common problems you may encounter, and how to solve them.