Rickie, the graininess is most likely coming from the surface you’re drawing on rather than your technique.
Plaster picture frames usually have a much rougher texture than drawing paper, so the graphite sits on the high spots and creates that grainy appearance. That’s actually quite normal. Even with the texture, the glass is still reading clearly, and the reflections and shadow are working well. If you want smoother transitions and darker values, try drawing on smoother paper such as Bristol Smooth, hot press watercolor paper, or smooth chart paper. Keep experimenting though. It’s always interesting to see what different surfaces can do. 👍