I keep my ink bottle within easy reach, along with scrap paper next to it. I dip my pen nib partway into the ink to fill the reservoir, stroke a few short lines on the scrap paper until the thin lines are crisp, then start working on my project. You'll want to place scrap paper over the lower part of your page to protect it from hand oils.

I often use a simple, slanted lightbox I made myself. See that section if you are interested.