---Multi-layer Keying in After Effects Part 4 - Creating Variable Width Edge Feather With Mocha For AE
In this tutorial (which is included as the last part of his series on multi-layer keying) Andrew Devis demonstrated a really nice feature in Mocha for AE (a free program that ships with After Effects).
This allows you to create a mask or matte with variable edge feather such that some parts of the mask can be created with very thin feathers (or even no feather at all) while other parts can maintain as wide a feather as needed for your production. Andrew also shows an option for a paid-for plug-in for After Effects that can achieve the same thing natively inside of After Effects and could be very useful for those who do a great deal of mask creation.