I thought basting spray was water soluble? Doesn't it wash out of your quilt?

This is what I thought. I would just try to wipe it off with a soapy rag. If you have duplicate rulers spray the same spray on one of them then just try to wipe it with a damp cloth then a soapy one, gently.

Likewise .... while I am not familiar with the Dritz brand, for other basting sprays, all it is ever taken was good ol' soap and water!

If it won't wash off use the product made to remove all sticky, stuck residue. It's called Un Do. It's what pros use to remove photos stuck to frame glass without harming the photos. It use to be impossible to buy or even know about unless you were in the business but now easy to find at Walmart. :)

Caution in using WD-40----might take off markings. Go slow in anything you use, just to be sure it does not remove markings.

Baby oil also works very well for sticky glues stickers and pine pitch.

I don't understand whether or not basting spray gets washed out of the quilt. If it is this hard to get it off a ruler, it seems to me that it must stay in the quilt.

Some of them, like 505, are water soluble. Dritz is not water soluble. Dritz recommends cleaning with a "petroleum solvent". Paint thinner or mineral spirits would be 2 examples of that. Actually, though, the first thing I'd probably try would be liquid laundry detergent (or a paste made with powder detergent if that's what you have) as it's not as harsh & is also designed to break down oils.

Dawn dish soap and a non scratchy scour pad worked for me when I sprayed my ruler.

I used alcohol on my acrylic table insert. It's clean now!