This is the place to share anything you find useful or helpful for making 6x4 content :)
I've put together a little content pack of tone swatches and gradients, printed out from my Label Maker. This shows off the sorts of dot matrices it produces, and the variety of tones it produces where digitally a shade is flat.
This may just be my machine and configuration, but 0-60% opacity produces varying shades of dot matrix, 70% produces solid black with a wavy texture and 80-100% is all the same tone of solid black.