I can't believe anyone would try to wash an old quilt in the bathtub. Even if you drain the wanter then try to squeeze out most of the water out of the quilt , it would weigh a ton. I wouldn't have enough towels in the house to try to blot the excess water out. Hanging on the line or laying out flat to dry would take so long.
I don't have a sensible suggestion for getting the odor out, but I have hung dry quilts on a line outdoors, especially in winter.