The best way to train unusual attitudes (in French "positions inusuelles") in IMC is VMC aerobatics once again
That may be so, except some aerobatic aircraft do not have an artificial horizon. Ideally, an instructor training a pilot on aerobatics (for the prime purpose of equipping said pilot with the skills for recovery on unusual attitudes in a future type), would demonstrate (say) a stall turn and during the entry and recovery tell the student to compare what he sees visually with what his flight instruments are displaying. That makes it easy for the student to correlate the two (visual scene and flight instrument scene). Same with a loop, barrel roll and so on.
The advantage of using a full flight simulator to teach U/A recovery techniques is that a competent simulator instructor can "freeze" the manoeuvre at any point - including fully inverted. With the scene "frozen" it allows the student the opportunity to more closely study the various flight instruments indications rather than have to work so fast to assimilate everything within a critical few seconds. The Sky Pointer is the key to getting the wings level as quickly as possible but it is quite surprising how many pilots do not know or have never heard of its use. This is an indictment on the pilots elementary instrument flying training. But it is soon rectified with appropriate simulator instruction.