1. Silver Metallic MMud (circa 2003) is essentially what Bud is describing. It produced the first "light fusion" of sorts, but was never called such. Application issues with the OVERLY thick Behr SM led to the early use of Mylar, then Glass Mirrors, then Acrylic Mirrors. These apps however required a Spray job. But for a spell, it was acknowledged that the SM basecoat did a wonderful job of both increasing CR levels as well as ambient light viewability. But why bother with trying to mix "Glitter" into paint? Such has been attempted several times before with pretty dismal results. (spotty, non-uniform mixtures) Using the Delta SM should be strongly considered instead these days for it's of a lighter hue and easier by far in "roller" application potential than any special mixture of seperate components or the Behr SM. Cheaper too. But if you roll on the Top Coat, it had better be in thin coatings using a VERY low nap roller. Apply the paint until you "think" you cannot see any trace of the underling SM. MMud already had pearl in it, but also Deep Base, so a new mix with more "White" or some RGB induced Grey might make coverage a little easier than the translucent MMud.
2.OMG. Do NOT consider SS on a Mirror. It is FAR from neutral. A Bombidil Neutral Grey darkened slighty would be far more applicable.
3. Rolling a mirrored LF screen IS doable if you use Foam rollers, and dry-roll on the first coat. I've done two bigguns before in Indy, as well as two in Memphis, and made comment that thinned BF mix rolled quite nicely sometime ago. But as in any such endeavor, the skills of the painter will determine just "HOW" easy or hard it wild be. Also, knowing when to stop painting, on a mirror or any other substrate, is the key, not the ability of the paint or substrate to deliver the goods.
4. Best of luck with the First surface approach. As far as I know of, I'm the only one to accomplish a working prototype of a FSLF, and it gave me absolutely a terrible time of it. 3 redos of various thicknesses of coatings...ALL sprayed, before I nailed it. The efficiancy you speak of Bud is not a freind in a FS application, for it really only increases the probability that you will not hit the right degree of opacity before you go beyond it. And that was with "spraying" and it's more precise laydown characteristics, But in retro-think, I never had the luxury of using a darker hued "Grey' paint, or one like BF with RGB and other ingrediants to mitigate the intensity of both the projected light as well as any returning light.
But also, as far as up to recently, FSLF images posted on AVS were hands down the best ever presented. No one disagreed with that, and that alone speaks volumes on this forum. But as sated previously, it was a royal PITA for me to produce, and would have been prohibitively expensive ( Plaskolite 'donated' to me a 4' x 8' Plexi FS Mirror that would cost $400+
So just as soon as I posted the images, I also strongly advised the app be dropped from consideration. Since then, Mylar, and aluminum, both polished and matte have been tried, with varing successes. And some abject failures too.
Applying any paint onto a FS Mirror involves doing so on top of the special protective-transparent coating that a FS Mirror MUST have to protect the silver coating. It does not want to allow paint to "tooth" so the first layer must be exceedingly thin and dusty, and with the thin to almost watery mixes we are now using, not getting a run or drip will be pretty hard to avoid.
But go for it. Just be advised....................