My advice.. for what it's worth, is to fly actual IMC, as often as possible.
'Under the hood', is OK, but not a whole lot more educational, than what you can drill into your subconcious practicing instrument procedures in the sim (
with good hardware). It's all good, but nothing makes you put (and learn) all the knowledge to use, and commit it to instinct; from weather-stuff, to flying holds; like planning for, and flying in, unforgiving, REAL conditions.. where you cannot see past the prop, and ice CAN happen, and being IN a cloud can turn you upside down, instantly..
It gives a whole new reality to the theories tested on a written exam, and makes wrong answers stick out glaringly ..