The Foundry has some awesome tools for denoising footage, I tried it recently on a 4K RED sample shot and it worked beautifully; granted it slow everything down to a crawl - but you can disable it while working.
I’m not really sure how it worked internally, all I know is that you have to select an area of footage that is flat (no detail), grey’s, and blacks work the best and you basically select an area and it computes that patch; the bigger the patch, the better the result.
The rectangle masking objects from the new tile-branch would be excellent for sampling areas - after that I suspect it’ll become rather challenging, I’ve no idea how they work. Do they take an average of the background colour, and the high-gain / noise and then figure out what percentage of blur to apply, and to what degree for each colour channel?
I can’t remember what channel the RED has the most noise on, but I suspect that it’ll be the blue channel, and if you could average out the noise of that channel in order to mute it, then you could probably get the values from that result and invert them to apply a full-screen noise effect at the end of the comp. setup.
P.s. It would be handy to have paint tools in the compositing window to paint over frames (and have reference frames in order to paint & hold patches over several dozen frames… matched up by tracking data of course for camera movement).