The fastest way? Perhaps sort it into groups, like:
Greens
Batiks
Calico
Reds
FLorals
Kids
Aquatic
^^^Something like that. See how much you can stuff in a FRB ($10.70 for the medium, $13? for the large) and then set a fair price for it. If it's "wal mart" type fabric, perhaps $2/yd is fair. If it's quilt shop, maybe more.
I'd say take a picture of the whole group before you stuff it in the FRB, so people know what the "greens" lot looks like.
Also be clear about how it's been stored. People are pretty ok with things like "It's been in the attic" or "We have a cat, you may see stray hairs on it"
With that much to sell, I'd say make an announcement on which day you will be heading to the post office. ANd then just pack, pack, pack for the rest of the week.