For the benefit of anyone googling in the future, here's some notes on bleeding a classic c900 Saab 900 heater core cooling system. (above is google-fodder keywording)
As suggested, the key is both to have the car up to _full_ operating temperature, and to rev the engine while the bleeder nipple (on the thermostat housing) was open. In order to keep the mess down, and to prevent possible siphoning of air into the system, I used my trusty "clear hose on the end of the fitting" method, looped that up over the open edge of the hood. The liquid came up a couple inches while revving, the bubbles came out, and when I got no more bubbles out I closed it off. No muss, no fuss, no spilled antifreeze, and I now have the expected "more heat than I need, by far" situation that Classic Saab 900s are known for.
Thanks for the comments. I really like this car ('86 base model 900). It's a bit rusty and has a few dents and scrapes, but it's _comfortable_, like an old pair of sneakers that's worn in _just right_.
Dave "waxing philosophical, since I won't be waxing that car" Hinz