Hello BRYAN M WOLFE , I just tried using method and it is not working .
1) My Set up is as follows : Macbook 1 + Powered Belkin USB hub + HDD 1 ( photo library ) + HDD 2 Time machine .
2) Macbook 1 has limited space so photo libary 650 gb is on HDD1
3) HDD2 time machine backs up MAcbook 1 + HDD1
Now i have 3 more Macbooks and the intention is to back up Multiple macs on the same HDD2 as per your blog.
4) Shared folder settings pic
5) shared Folder settings pic
6) Take note the Final Back up is actually the HDD2 . It does not allow me to create any folders .
7)Now I will move to my Macbook 2 and Finder and then i can view Final Back up Folder with 3 grey person image
8) I go to Time machine on Macbook 2 and select Disk and then Select Final back up folder and start back up
9) there is an error that you do not have the necessary read write and append privilegee .. refer pic
I have done this again and again in several different macbook and still same error . I have contact apple care and still same error . Finally one senior apple care consultant told me that since i am selecting a HDD thats why it is not working i must select a Folder . however i am not able to create any folders on the HDD2 which has the time machine back up . Hmm i am lost . Kindly assist pls .