This is a tricky one to set up, but it's a great feature because, as you point out, it lets you consolidate multiple phone lines into a single ringing device and, even more usefully, a single voice mail system. The only thing I wish I could do is have the phone ring on the original line two or three times before it forwarded, because then you really could have a permanent call forward and still grab calls if you happen to be in your office. As far as I know, that's not an option though.
On to what you're asking about, however!
To remotely set up call forwarding (actually, Qwest calls what we're talking about call following) you need to be at the line to which you want the calls forwarded then, either from that line or a different line (e.g., your cell phone), dial up
888-xxx-8052
where "xxx" is your area code. If you're in San Francisco, it'd be 415, and if you're in Denver, it'd be 303.
Once you're connected, you'll be asked to enter your own phone number, then a security code.
If you haven't yet set up your security code, you can use the default of 1234, at which point - no surprise - it'll ask you to set a better, permanent code. I'd do that straightaway if I were you!
Now, you'll want to go to the "call following" setup area (option 1 on my local Qwest system) and enter the number to which you want the calls forwarded.
Here's the tricky part: The system will then actually call that number and you need to answer and accept the forward before it's enabled.
Once you do receive and indicate your acceptance of the forward, it's then in place until you cancel it, be that an hour or a week. Nice!
Now if we could just have it ring twice on the original line before bouncing to the call following number...
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This is a tricky one to set up, but it's a great feature because, as you point out, it lets you consolidate multiple phone lines into a single ringing device and, even more usefully, a single voice mail system. The only thing I wish I could do is have the phone ring on the original line two or three times before it forwarded, because then you really could have a permanent call forward and still grab calls if you happen to be in your office. As far as I know, that's not an option though. 
Even easier than that is the basic call forwarding that you have set up already. Just dial *72 from the phone you're forwarding from, listen for 2 beeps and a dial tone, and dial the number you want i forwarded to. You will then have to answer the phone that you are forwarding to. When you want it turned off, just dial *73 on the phone you were forwarding from.
Be forwarned, however, that if you are forwarding to a long distance number you will be charged your standard long distance rates on that call.
And Dave, what you described is a Call Forwarding \ No answer line. Similar how calls are routed to a voicemail system after a determined amount of rings, you can have it forward calls instead.
Hope this helps!