p4 protectcommand through Windows' Cmd Prompt. I couldn't come up with a way to update the Permission table in a manner that I could automate later. For instance,
p4 protect -idoes allow standard input to be rerouted to the Permission table, but I don't know of a way to insert that data from, let's say, a text file that has the intended Permission setting.
An example of my intent is:
Permissions: super user Me //... write group SomeGroup //...
Permissions to be updated to:
Permissions: super user Me //... open group SomeGroup //...