Have you sat the guy down and asked why he appears averse to this additional training requirement? Might explain his thoughts as to why this is a chore to him.
Not directly but I have probed in the area. I think his resistance is two fold.
One is he considers NVGs to be the silver bullet to inadvertent IMC...while I do not. I see them as a useful tool but I remember well a training incident in the Army. We were conducting low level ops and by the time with the goggles we realized we had decreasing visibility we were in the !!!!!. I was grateful I was a sharp instrument pilot for the recovery.
Second is a combination of decay of his instrument skills ( the amount of instrument training in most Air Ambulance operations is, in my view, inadequate) and coming from glass cockpit to analog. He has been mostly flying EC-135s and EC-145s the last couple of years and we still operate a BK. I found it very easy to acclimate to glass...but not the other way around.
The good thing is both my other pilot and my mechanic are excellent instrument pilots as well as ATPs and I expect they will have a positive influence...