I was a passenger in a Beverley trainer out of Singapore up to Okinawa and Hong Kong way back in the early 60s, when I was flying helicopters in Malaya, and somewhere over a lot of water they shut down both engines on port side. Engineer disappeared into the wing, emerged after some time, and I'm sure some loss of height, before crew unfeathered and restarted both and we continued happily on our way. I gathered it was to top up oil ... is this feasible? Whatever, I was well impressed.
Engine oil pumping in the air was SOP for the Beverley. Though I never heard of the requirement to feather the engine.
It was done by means of a manual operated pump in 'the dog kennel', just aft of the flight deck.
Flt. Engineers that didn't top up in flight, were unpopular with groundcrew.
Standing upright was not possible in the kennel, so operating the pump in a crouched position was hard work.