Analog film photography and cameras

A question that has been lost in my earlier ramblings:

How do you emphasize / add grain to a scanned image?

I've used SilverFast at the scanning stage and Corel PhotoPaint to adjust gamma, brightness, contrast, intensity, saturation etc., sometimes over the entire image, sometimes in a masked area, but can't see anything obvious that would give the impression of changing grain size or density. I'm guessing different software might be needed? - and possibly posting in a thread I haven't found yet?

You don't you do it when you're processing the film.