Installing Stretch/Testing with absolute minimal bandwith useage

[Richard Owlett]

I am running Stretch that was fully updated/upgraded less than a week 
ago. I have the flash drive used to do the original install of Stretch. 
I have not _intentionally_ purged any files from cache.

I wish to install Stretch on two additional machines. I am near my 
internet data cap and wish to make *ABSOLUTE MINIMAL* usage of available 
bandwidth.

The purpose of this is to test the _installation process_ itself. That 
eliminates anything resembling cloning. A secondary benefit will be 
learning more about how Debian does things.

Suggestions?
TIA