"None of the GPs did anything for 10 seconds..." Interesting observation; I've often suspected that they didn't do much for the first few seconds. Seems like a "short" application, less than 30 seconds or so, did nothing. Guess maybe that's why.
If I haven't had it on the block heater, I most always hit 'em for at least 30 seconds, more if it's relatively cold- maybe almost a minute. And sometimes that doesn't do it; if it fails to fire up fairly quickly, I'll re-apply glow for another 40 seconds or so. (I don't want to be replacing starters!) When it gets near or below zero, I use the block heater for at least an hour; then it fires up almost immediately with little or no glow.
Can't wait to test out the belly pan heater on the transmission (it's on now, and we have pretty heavy snow coming down....) -- like Ray said, warm to the touch; should reduce hydraulic warm-up time quite a bit, I bet.