A little backtracking. I really, really didn't want to mess with fire, all joking aside. So, at the very beginning before I messed with any pipes, my plan was to turn off the gas at the furnace, turn off the gas at the water heater, TURN ON THE DRYER, the appliance furthest from the meter and make sure it was blowing hot air. THEN I went outside and turned off the gas at the meter. My intention was to bleed/burn the gas lines dry. I ran the dryer until it flamed out and ran cool, then I turned off the gas at the dryer too. Then, I began the pipe install by removing the nipple/cap.
Now, back to the present. Having verified that my plumbing work was gas tight (and the valve was shut in the kitchen and the top of the valve stuffed with a paper towel to keep the dust and crap out, I turned the gas back on at the dryer and started it. It worked. I followed the procedure for relighting the pilot light to the water heater, I could not immediately test this, since it takes a lot of water moving through my pipes to cause the water heater to kick on. The pilot was clearly on, so that was good enough for now. Lastly, the furnace.
I turned the temperature at the thermostat waaaay down, like, 48 degrees. I had Twil standing by at the thermostat. I went downstairs and took off the access panel to the furnace.
I turned the gas to the furnace on, and hollered for Twil to raise the temperature on the thermostat, to say, 80 degrees; heat it up!!
Then the gas turns on.
Now the motor to move the air up the exhaust stack starts spinning, then the igniter starts to glow.
Then it starts heating the house. Success! I put it all back together and moved up to the kitchen.