My pre-heater works. Yes, do pull the throttle handle out a few clicks first.
As often happens, I read the instructions way too literally and was initially operating the thing incorrectly. After heating up the glow plug and flaming some fuel through it, keep the pressure up and crank the engine *while* some fuel is flaming into the intake. The instructions tell you to keep pumping for a period of time even after the engine has started.
How easily the engine starts is dependent upon the condition of the engine and the fuel system. Seriously, step away from the ether if at all possible.
FWIW, my truck will start easily down into the teens if I just use the flame heater properly. (I haven't had a chance to try it in single digits and it doesn't get below 0F where I live).