There are 4 ways to do this off the top of my head:
1: Be on a LAN (Local area network) so you can simply /devmap [MAPNAME] on the first PC, then on the second PC type /connect 127.0.0.1 and it should connect to the server you just created.
2: Buy your own server, of course this would be the simplest option, but a waste of money for just creating cinematics.
3: Create 2 4D1 accounts and adapt it to this tutorial, it wouldn't be with your friend(s) of course, but you get the idea.
4: Find a tutorial on YouTube on how to create your own cracked server using your PC, I know there are plenty for COD4, I don't know about 4D1 though.