You don't need to live in the gym. My clients typically have half an hour twice a week with me, total one hour a week, compared to the 5-12 hours you're talking about. It's all about intensity.
Doing the same routine on your own it'd be a full hour twice a week, or better three times a week, for 3 hours. You just have to get your arse into gear working properly. That means focusing on - you guessed it - the big compound lifts, squat, split squat, front squat, powerclean, deadlift, bench, row, overhead press, inverted rows or chinups, that sort of thing. No faffing about with curls and crunches.