This is how I remember the old files going. i think there was even a tutorial but I didn't ever do it.

If I remember right you swapped the geometry in the cr2 for the other geometry. So, for shoes, you will take your characters feet obj reference and swap out the shoe reference. At least, that is what I think happened. Thinks like kirts and stuff would be harder if it didn't fully cover. You can also export the figures out as a single mesh and then recut and rebone the figure.