Additive Keying or Using "Spill Merge"

I'm getting stuck with the blending modes when trying to add "fine" detail back into a key. Especially with motion blur keys. I've used the "Spill Merge" macro from Stefan for reflection surfaces and it always turns out great. What I'm trying to do is preserve the detail that the Spill Merge Macro has in hair and motion blur and place that back over the top (or under) of my core matte. Maybe there's a better way to approach this, but I can't seam get the background to match the graded plate I have when using this technique. Any help is appreciated.

Here's a link to Stefan's marco if anyone is looking for it.

http://www.comp-fu.com/tag/fusion/page/3/

Hey Ryan, I am not sure an additive approach would be correct for edges, reflections by nature are additive light, so dark colours are less visible, light colours more visible. If you use this for edge detail it means darker colours (say brown hair) would be less visible than say highlighted skin. I don't think this method is appropriate for MB or hair, you need to be generating an alpha channel to get the correct detail back in. I often manipulate the edge colour manually on areas of MB/Hair sometimes even paint in solids to use with the edge alpha to get best results. Apologies if I have misread the question.

Thanks Kel,

It's probably more of an effort on my end to have to roto different sections of the key, and treat those areas separately. What I usually run into is the de-spill looks great in certain sections but not in other.

Example: a brow hair key with heavy motion blur looks great over a background that is lighter than the hair color, but get's "halo" around stuff that's darker than it. Usually I do a color edge extend or pipe the actual background into the despill process to help "color" the edge, plus a lot of roto. I think I just get spoiled using Keylight, where, most keys I can get a great looking key with only 2 or 3 instances of the the effect. When I key with ultra keyer, I end up having to use 5-10 keys to get what I'm after.

So, I was trying to find a way to "add" that subtle detail back from an additive keyer, but "multiplying" or "screening" the additive sections of the key where it over laps the darker areas. Hope that makes sense. Thanks for the feedback.