I print out my label on paper using the fonts, spacing and wording I want. Then I lay my muslin on top of the paper and put the two together in an 8" embroidery hoop to tighten it up. Then I plop the hoop over a 7½" round marble trivet that I have that gives the fabric a solid backing. After that, I just trace what I printed. Works for me. I have found that the slower I go, the better, and the thicker (at least 05) Pigma pens work better. I think the nibs of the finer ones get hung up on the fabric threads and skip.
I learned early on that I wasn't cut out to do them freehand! Maybe you could try signing your name with a Sharpie on a piece of paper and then tracing that onto the muslin?