Although we have a home network so that any computers are connected to wired Ethernet and can share the networked printer and scanner, I do not usually have my backup computer on at the same time as I have my main work computer on. So I'm not transferring files from one to the other over the network very often. For fast backups, USB flash drives are great. I've seen the term "sneakernet" used. Copy a file to a flash drive (being sure to wait until safe to eject it when it's finished), and walk it over to another computer to copy the file to that one.
We just have to remember to do this consistently.