AutoUPnP will automatically open and close your server's ports when needed (meaning while it's on).
There's no need to do anything on your router's interface other than turning UPnP on (Which usually, by default, it is). No need to know the password. Simple and quick.
Commands
Open port: Usage: /open-port <InternalIPv4> <internalPort> <externalPort> <Protocol> <Description...> Example: For this example our internal IP is 192.168.1.100
Code (Text):
/open-port 192.168.1.100 25565 25565 TCP Minecraft Server
Now port 25565 is forwarded
Close Port: Usage: /close-port <Protocol> <external port> Example: We'll use the previous example and assume port 25565 is open.