Just came across this post.
In regard to reel numbers, when I clicked on the Georgia census shown on the results page from your link, there was a list of Counties with the reel number associated with them when you scroll down the page. Go back to the results page to find the correct reel number for your state. Hopefully that will make it easier to find the reel needed.
Caveat: I did not check others to see if they were the same.