Did he also tell you to throw away your dark frames and just hope for the best? Short subs are great if your mount is drunk, but 500 of them on Andromeda is like mowing your lawn with nail clippers. You still need enough exposure per frame to get above the read noise, otherwise you're just stacking 500 piles of gray mush and calling it data. Your 3 minute subs worked because the camera actually had signal to work with. The real answer is it depends on your tracking, but anyone saying "always 500 short ones" is probably the same guy who swears by a $30 tripod.

Ha! Bracing on a column beats a flash any day, but have you tried a tiny flashlight aimed up?

Spent 3 weekends fixing water barrels when I could've just read the directions once, so I feel your pain. My version of "one step" was forgetting to clean them before filling, which taught me that shortcuts always cost more time later. At least now we both know what not to do, even if we learned it the hard way.