Greyhounds, because they are built different than most dogs, aren't really able to scoot comfortably! When our dogs sit, their butts don't even touch the ground!
We haven't had any problems with impacted anal sacs (yet) with any of our dogs currently, but my old cocker spaniel (who scooted ALL THE TIME) had to be taken to the vet several times to have her anal sacs expressed, or drained.
Funny story while we're on the topic : last year we had Paula at the vet to have a vaginal problem checked out, and while the vet was crouched back there, poking and prodding, nervous-ninny Paula "shot" her anal sacs all over the vet!
The fluid is so foul-smelling, not like poo but like a really sour, heavy musk - that examining room probably smelled like that for days - and I don't want to know how many times the vet had to wash his lab coat!