Because the Spatter filter only functions on contiguous pixels, there is no simple way of applying it like a Smart Filter to a layer of line work.
I'm looking at the work of Kevin Dart, and trying to replicate that chalky line, but in such a way that I can tweak my linework separately to the spatter effect. I've got as far as using a Smart Object with black linework over a white background layer, then applying Spatter Smart Filter to the Smart Object.
But the next step would seem to be to use the Smart Object as a clipping mask. Except that I need to mask based on the Black/White layer mask method, because I have all my pixels opaque.
If I go turn off the white Background layer, the Spatter ceases to function.