I was lucky with mine. Having done similar trips many times before in both IMC and VMC 2 crew. Once I completed my Single Pilot Line Check and was cleared to line on the S76A (Hamilton Standard Phase II) IMC /SPIFR flights to rigs were quite routine.
I believe my first one was actually night IMC from North Denes to a diving support vessel in the Esmond field called the Bar Protector. I carried out what used to be called a rig radar NDB approach and found the vessel without too much difficulty. It was raining and windy.
The most difficult part was the cross cockpit landing on a moving deck in the dark. At least I had power in hand with the wind. I think that the 9 guys in the back were quite relieved to be on the ship! After that, it was off the Newcastle to drop the inbound pax then back to Denes.
We used to do night Amoco shuttles with a crewman almost daily in winter and it was not uncommon to plan IFR on those flights, especially after a few days of fog when the client wanted to get the trip done, even with a poor payload. Then there were the night Rowan Crew changes once a month.
While it was busy and one had to concentrate hard, the Bristow training in those days was excellent. We did so much night flying in both IMC and VMC that it was kind of routine. I think that there is a lot of value in training but also in being practiced at what you have to do.
Would I do it now?? No, probably not, too old and, quite properly, risk management would dictate otherwise nowadays.