The instructions look very similar. But did you check the different sections to see if there's a Universal Plug & Play (UPnP) option? If not, then you "should" manually port forward.

As far as choosing ports, the default is 6346, but if you want to go for a safe port, look at one between (49152 - 65535). But as I said, you're still going to get the firewall issue "unless" you manually port forward or enable UPnP.