Shy, the RAF SAR Force is well versed in mixing white light and NVG and you are right, winching on purely NVG references is less than ideal since the relatively poor visual acuity (20/35 at best) on goggles means that very accurate positioning is difficult so white light references are preferable.
The problem is when to transfer from NVG to white light and that depends greatly on the conditions at the time - light levels, cloud, rain etc - we teach pilots to approach the scene on goggles and switch on hover/flood/steerable spot lights to see how much 'blowback' (like using full beam in fog) they get.
Sometimes you can get a good white light picture early and use that to establish the hover for the recce, sometimes you end up completing the recce on goggles and only switch to white light fully just before winching - it depends on the situation and available references.
This where being able to open the cockpit sliding door (a la Wessex and Sea King) really helps - shame that isn't an option with S92 or AW 189!
Over the water for a very small vessel or a person, an NVG hover is often best (if HT/AHT isn't workable) as it often gives you a decent visual horizon to work from - again it depends on the night and the wind (light winds leave you in a recirculating ball of spray which is horribly disorientating on NVG).
Because of the variability of the conditions, a lot of training is required, in different conditions, to make sure the crews can deal with whatever they are faced with. A short 'here are NVGs chaps, it's just more hovering' course might look OK on paper but really won't be adequate unless you are just ticking boxes.
Add in the fact that many flights have to deal with everything from flat calm overwater to ****ty conditions in blowing snow in the hills then you can see that a proper NVG training package will be required.
Hopefully the goggles on the new SAR service will be at least as good as the NG700s currently used by the SAR Force.
Crab's Law - like it. It usually starts with name calling and personal insults before the 'outing' but I have pretty thick skin.