I can only imagine how frustrating this must be for you @KS Cookies!! I also airbrush my cookies a lot and package them by heat sealing the day after they've been airbrushed. Before I box and ship my cookies, I put each heat sealed bag (with ribbon) into an individual bubble out pouch to ensure safe travels . I have several clients who request my soft sugar cookie recipe along with my RI recipe that has a softer bite (doesn't dry rock hard so no rubber stamping on these guys).
I've never had this problem in the 4+ years of selling decorated cookies. Clients often send me pics of the cookies at their events so that I can see how they have been "presented" to guests. I love seeing that . What airbrush color brand do you use? I use Americolor and often use black. My lines remain clean, no smudging. When I use an edible food marker I will see some smudges if I touch the area where I used the edible marker.
Wish I could be more help! Do you live in a humid climate? I live in a very dry climate which may contribute to not having any smudging issues. I don't know . I wish you the very best in identifying and eliminating the issue. ❤️❤️❤️ Hugs...