I've only seen the settings for a couple of routers, but they seem to have a gaming mode, a DNS setting (to host you need a static IP, or do like I do and get the free one at dyn.dns.org).
Then just open the telnet ports.
Tell him to look at his router, in the back or usually underneath and it will tell him how to access his settings. Usually pointing a browser to 192.168.1.1 then entering the user name and password to access router settings.
Once you have the router settings look at the TWGS configure settings. I'd have to stop my server to give you more detail here, and you're logged in.
