In terms of getting their attention it's as simple as emailing them, explaining what I do, and giving them the hidden zine page so they can all the past issues. (or DMing them in the rare case they don't have an email) I also contact them about 4 months before the issue's release and have no instructions other than including the word "Indiepocalypse" so the commission is both easier (since they complete creative freedom) and they have plenty of time to fit it into their schedule.