20grit

Since you're silk screening them, I'd attempt to test some different thread counts in your screens. Use your precisely traced vector art, then roll from there. If there is any imprecision I see in older graphics work, it is generally due to the execution (being things like screen thread count, moving screens, etc.) and not the design. Lower your thread count some, and I'm willing to bet you'll start to get more of a warm, fuzzy, 'authentic' feeling about what you're producing.

That is assuming you have a screen set up where you can replace the cloth. I made the mistake of getting a frame with an adhered screen once. What a waste.