Diffusing at the enlarging stage produces anti-glow--the shadows bleed into the highlights. If you do it very subtly, usually with a mix of exposure with diffusion and without diffusion, then you can get a reasonable softening effect. If you overdo it, it becomes kind of ghoulish. In either case, I wouldn't call that a glow.
To get the highlights to spray into the shadows, which I think of as a "glow", you need to do it when you're making the photograph, and Mike Johnston offers many fine suggestion in his article, linked above.