I just wanted to confirm one thing real quick. Is it just the amount of grain that you're complaining about and want to improve? If so, there are software tools built into some scanners that help to remove grain. But these tools also soften the image in the process thus requiring more sharpening later. Does your scanner come with any "grain reduction" modes or tools? Did they make any difference for you?

If your scanner doesn't have these tools or if you've tried them and they don't help then there's not really much you can do.

Often, in color images, the grain is mostly found in the blue channel and not the others. Knowing this, you can sometimes clean up the blue channel a little bit and improve the graininess of the image.

Something else to try might be to scan the image in the highest bit color mode the scanner supports and then convert the image back to black and white through software like photoshop. It's possible that the grain will be less pronounced.

If all of these methods fail, and any other similar variants you're able to think of, you might want to try switching over to a slower speed film. I had really great results scanning Delta 100 on my Nikon LS-4000 scanner back in the days Really great detail and great grain levels (hardly noticeable).

I hope this helps put you in a positive direction!