For strength, I wanted everything coated in the cookie icing, which dries harder -- close to a royal icing. I just followed the heating directions on the bottle, and then squirted some between each cookie, then squirted it on the outside and went over it with a paint brush.
After that got good and dry (bottle says wait 45 minutes), I made some gray butter cream. My original intent was to completely pipe over the coated cookie, but it was just too difficult to get the piping bag into the nooks and crannies.
When I was wiping off the buttercream, I found that I really liked the 2-tone effect that the half-wiped-off buttercream gave, so I just squirted buttercream here and there and swiped it across the cookie until I was satisfied with the overall coloration. I like the way it turned out; a happy accident!