Several masks on one layer?

Hello:  I am one year in as beginner on after effects.  I am interested in projection mapping my house and have found several good youtube videos on how to do but...I came across one video where they masked a little dollhouse.  They end up with one master layer and 80 masks ON that layer.  I did find out how to add masks to one layer but I cannot figure out to animate one mask at a time. I do know how to "add" to show the mask.

 Thanks in advance for any help.

V