Offline Staging

I'm very certain this is not unique to the world of small model railroads, but I thought offline staging would help save space. In traditional staging you have fiddle yards to the side or behind. I don't have room for that right now. My solution? Use the NP mainline as staging for the yard. Cars waiting for pick up are placed on the main, when their time comes 0-5-0'd to the appropriate yard lead for switching to their destination. I plan on only running around 12 total cars on the layout so they'll all fit up top. But once my waybill system is implemented I can sort cars on and off staging and not worry about space. I'm still not sure how to implement waybills. More reading is needed indeed.