Hi...how do you get a rustic box look from buttercream? Do you spread the darker color around in random spots and then smooth out when icing and then use a cookie scribe tool to etch?
W/o a airbrush that’s what I would do. I’d probably find something to emboss the icing rather than score it - there must’ve something that could be used
I cannot visualize the design you are describing, so no help here.
another way if using crusting butter cream after using a fork or whatever for the texturing and it's crusted, dust it with cocoa --
but otherwise yes adding piped lines of darker colored icing before smoothing is good way -- you could dust after that too --
I think you could gently dust on cold Swiss meringue icing too --
Oh good idea using a dusting of cocoa:)