What exactly is proxy skinning? Like using any other proxy, you are able to work on the skin weights of a mesh through a proxy object, or some representation as a substitution. The substitution doesn’t necessarily need to be a lower resolution version of the original mesh, but it can be in some cases. It is all about keeping the detail in the skinning process, while making it easier to create weights and iterate within the rigging process.
Showing some examples of how proxy skinning can help you in production is Sean Nolan. Sean shows how a proxy concept can really help out for quick iterations with skinning, or as a solution to some skinning and rigging challenges with certain source geometries.
The tutorial shows using some Proxy Skinning Utilities code, that Sean makes available for download.