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.

I have recently used a Quilter's Dream poly batting (I'm usually a cotton batting person) . I basted it with washable Elmer's School Glue and it has stuck together well. I did spread out any heavy drops so that they wouldn't dry as chunks. I left it to dry overnight before I moved it from the tables I baste on. I am currently quilting it on my dsm and am not having any problems other than my less than perfect quilting.

I use polyester batting from time to time with my glued basting and do not wash it before quilting in any areas. The glue comes out just fine after the quilting is finished. I have never had a problem.

I use poly batting for projects but rarely in my quilts. I use Elmer's Glue to baste it but put the glue on the fabric side not the batting. It works much better.

I use mostly hi-loft polyester batting. A few days ago I needed to add a thin strip of batting to get the length I needed. I put Elmer's washable school glue on wrong side of backing laid strip down, put a strip of glue on top of batting and laid edge of quilt on. I use large safety pins and pinned across the joining pieces, laid it flat and let dry overnight.
Next day I could not tell where it had been glued. Quilted up like the rest, no hard places.