Can you really though? I guess I haven't really looked into it, but from what I have seen all the post processes do is put a little band in focus and blur the rest of the image. With an actual tilt/shift setup you can put the focal plane at whatever angle you want, as well as control depth of field and perspective. All the photos and videos I've seen done in post look super tacky.
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I know people have made lenses capable of this by combining the end of a plunger and a lens for a larger format than whatever you have. The used 6x6 lenses for crop sensor digis. But if you're just after the miniature effect than go for the post processing option.