Most hands-off... hard to say.

You've got soil background so I'm tempted to say that Hempy would be the best way to transition to hydro, and it's a pretty simple and fool-proof system.

Beyond that I'd say DWC. No real moving parts aside from the air pump and maybe the timer, and air pumps run practically forever. If the power goes out or the pump stops for some reason you've got a little while before the lack of aeration becomes a problem, but you definitely don't want to leave it like that for very long.