This is good for me to know, NZ, I mean to try glue basting but I usually use poly batts. Spray baste has been my chosen method.
I'm with the others. The times I have dealt with washed flimsies makes me recommend (strongly) to not do it!
Not in this case anyway, the only times I will consider it is with bodily fluids/stinky/sticky stuff on the outside. I'm looking at you, cat!
If you ever really really have to, just treat everything super gently. Put the top in a large sweater/lingerie bag, do more soaking/swirling than agitating so gentle cycle in the washer. I often recommend hand washing fragile tops by hand in the bathtub, using a large cheap plastic laundry basket (with the holes in it) as an agitator basket, by dipping and swirling the basket up and down, and you can rinse while supported by the basket.
Never pick up a wet quilt by a corner to pull it out of the washer, the weight of the rest of the quilt will produce a lot of strain. I grab a couple random handfuls and lift up, then kind of scoop it all into the dryer.
I have some pretty bad dust mite allergies and have to wash my quilts monthly -- have had a lot of experience handling them.