Look on the bright side, now that you've had some practice doing the mackeral pattern, the next batch will look even better
Another thing to try, most craft stores sell those pens that use india ink, pick up one of those and a few tips of different sizes. Use the same createx paint that you use on your plugs as ink and draw all you want. The paint is the same so you know there will be no incompatability issues. You can use the same pens to sign your plugs too.
Jigman