I don't know if this info has been posted before (if so, I couldn't find it) but I thought I would share this with you as I found it interesting.
If you look at the girth on the Preproduction 1 Boba Fett Costume, you will see in some photos that the sling gun is held by one of the strands of the girth, which is pulling that strand out of place. It is interesting to note that the strand that is pulled is white in the area where it is pulled away from the vertical retaining lattice.
This makes me think at least on the Preproduction 1, the girth was painted, and not dyed.
Don't know if that helps, hurts, or makes a difference, but thought I would throw it out there.