You should outline directly on your cookie, so the outline rest on the surface of your cookie and seals it to prevent the spill. Somethimes in edges of the cookies there are small cracks, seal it before you fill the cookie. You don't need to wait to many time to dry the outline, it is dry when you end of outline all your other cookies, but if the weather is wet, you need to wait .
You can outline and fill in waxed paper, but cookies are not exactly flat, I use it only for small ornaments not the whole cookie.
Not all of us can pay for a Kopycake, but there is a how to do one for yourself in web using only a batery lamp, boxes and a piece of glass or something transparent. I used cardboard to build stamps to "draw" what I wanted to outline on the cookie. I use as ink watered royalicing to "print". You can use comercial stamps using endible paints for that too! Or cutters...
On a class I took they teach me to make many copies of the picture as needed, cut the outline, cut each individual piece alone and outline with a tooth pick (for cakes), but in cookies you can use a edible marker.
I hope I could help you. I'm not profesional, only a hobbie Baker (for birthdays and other family special dates and holidays).