router config/remote control

Out of Curiosity How does voipo handle people that dont know how to get in to routers etc to do the port forwarding? I think I read in another thread they were using some sort of remote control software. Is this vnc or something? I wonder what the best solution is for getting behind someones nat to configure their router might be?

We have been going back and forth between TeamViewer.com and InstantHouseCall.com.

The customer just runs a program on their computer and we use the password is generates to connect.