Photography: Camera sensor size difference

Makes sense. I presume the multicoating's party trick is to tame glare/reflections ?
Well, I need something to kill excessive light (I want to keep the aperture wide and ISO low), an ND would be the obvious choice (or a set) - but I want it to be infinitely variable (don't ask why!) - So I was thinking of stacking two polarizers a circular and a linear and turning the front filter to adjust the light getting to the camera. (?)
I also want something to stick on the front of my Nikon 80-200 f2.8 because it cost a small fortune and I am fucked if I scratch or otherwise knacker the front element. What do you reckon here, a UV or just a plain bit of glass (whatever they are called?).
I think I will stick to screw in circular filters for the moment.
Cheers for the info I will have a look on t' 'bay for some Hoya/B&W action.
Oh, yeah, nearly forgot, racist.

multicoating for reflections you can usuallt tell by looking at it if it's yellowy greeny magentary it's multi. just one colour it's single i think they usually have 'HMRC' or 'multicoated' on the side.

two polarisers? this will kill reflections up the contrast and change the colours are you sure you want to do that to the image? polarisers have their uses but their effects aren't allways wanted.

if you aren't using a lenshood then a good multicoated 1A skylight for the zoom.
as for protecting camera equipment? that's what insurance is for!