Lets start with your terminology. There is NO grain with your digital camera, none, zip, nada. Grain is the actual silver crystals on the film. No film, no silver, no grain. You are probably comparing digital NOISE to grain, which while they act and look similar, are two completely different things.
Next, there are several things that can affect how the grain looks. First is the type (quality) of film you are using. I love Ilford, even where there is grain, it is well structured. Delta 400 is good, HP5 is great although it does show it's grain a bit more, it is beautiful grain.
Exposure is the primary concern. Incorrect exposure can cause emphasized grain, make sure you nail it.
Next, developer. I tend to use Ilford DDX. While not a fine grain developer it does promote wonderful tones and great structure. Not to mention it is fast and easy to work with.
Then we come to the development. You have to mix exactly right, keep your temps exact, and use a digital timer if you can. Follow the directions exactly and if nothing else at least you can adjust other aspects and know that the development will be consistent.
Now to answer your question about different ISOs, yes, dropping down to Ilford Delta 100 will show a dramatic decrease in visible grain. Personally I prefer the look of Ilford FP4 at iso 125. Pan F at 50 iso is nice and pretty grain free although I don't like the tones as much as FP4.
Allan
PS. Also, when scanning in and processing B&W film, be VERY careful of sharpening. Unlike digital where you can cover up a not-so-sharp image to some degree with Photoshop sharpening, if you do that to a film image you will sharpen and amplify the grain!