My solution when I need to wash something BIG or a quilt that is BIG is to spend a couple of hours with my daughter and grandchildren. Like many modern moms she had one of the large water saving front loading washer and dryer sets. I load my quilt and we chat, drink tea and wait for the washer to do it's thing. Or as more often the case, I go over to her home when they are at school/work and I wash the quilt and partially dry it, then bring it home to lay out flat somewhere in my home.
Find a friend with a large washer, bring a yummy snack and tea/coffee and let the chatting begin.