My dog keeps scooting his on the floor even though he got his glands expressed already?

Just because his glands were expressed doesn't mean he's completely out of discomfort. It's possible the groomer didn't do it right, maybe they didn't completely empty the fluid, or maybe he had an infection before you solved his problem. Let him scoot for now, but if he's still uncomfortable in 24 hours maybe you should consult your groomer, or even the vet.