I just checked my oldest RAF logbook (I'm now on logbook Volume 6). Having carried out approximately 40-45 hours total time on helicopters we (as those of us in the RAF's training system) began our instrument flying phase. This was in floppy stick (very floppy) Whirlwind 10 helicopters, so the basics were ingrained at a very early stage. I've held a helicopter instrument rating ever since, now some four decades or so. In the past I've operated a "floppy stick" police helicopter for public transport under IFR and properly IMC (now not allowed in UK), as well as far better equipped, SAR helicopters with full auto-hover, approach and auto-transition to climb modes.
I'd say that any unrated helicopter pilot finding himself in cloud will struggle to remember anything he was told or read about! Even those who have been properly trained need to bear in mind that instrument flying is a very perishable skill - me too!
Even though I now fly a single pilot IFR machine, with a fairly capable autopilot, and routinely fly VFR- IFR- VFR (or remain IFR to land), I do take care to remind myself of that fact.