1. Have all players download
Hamachi 2. Have one player set up the virtual network in Hamachi
3. Make all players join the virtual network set up by that one player in Hamachi
4. Have one player (it doesn't have to be the one who set up the virtual network) start the host shortcut under the gog.com start menu folder for Redneck Rampage.
5. The game will start up the setup program which may seem strange, have the player who started the host game go to Network Game, set up how many players will be playing (and anything else), and launch Redneck Rampage. He'll now be waiting for players to join.
6. Start up the CLIENT shortcut under the gog.com start menu folder and it'll ask you to type CONNECT followed by the IP. So let's say your friend in the Hamachi network has the IP 5.52.136.134. You'd have all players who want to connect to him type CONNECT 5.52.136.134 and hit enter.
7. From there they will also have the setup loaded which is the same as the host's, all they have to do is go to Network Game and Launch Redneck Rampage.
Note that I've only tested this for 2 people using the original Redneck Rampage with the cuss pack, if you have more than 2 there might be more needed to do in setup, however I am certain this works as my friend and I bought Redneck Rampage and tried it out on Friday night by doing this.