So you want to get a film look, or an "old" film look?
Just the plain old film look is pretty easy, add a touch of grain, play with the contrast levels, I think FCP has a "frame" filter in the pallette.
For an old film look ( this is tedius but free) just do everything above but then go through your footage and cut out a few frames. This will get it a little jerky looking.
Well, that's all I got, seems to work OK for me.
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