1 ) Bake your displacement map, have colored diffuse already done
-Zbrush will only be able to edit 16bit disp maps
2 ) (Here’s where I screw up somehow) Load the displacement map and diffuse map onto an image plane, and play with displacement settings (which, for some reason, I can’t get it to do)
-You could also try fill canvas, under the colour menu, this will fill the canvas with the colour, material and alpha you have selected.
3 ) Capture the result, export as new map with funky effects.
-yeah either from the menus or MRGBZGrabber (although this may crop image depending on how much of the canvas is used).
I would also add
-resize your canvas to a square resolution 2048 x 2048 etc…
-make sure your uvs aren’t overlapping and give them a 4 pixel gutter/bleed.
-the plane is polygonal and therefore resolution dependent, with the fill canvas method you have no resolution dependency, and since the canvas can utilies the zdepth for 2.5D operations an alternative would be to use projection master to add further detail to your maps (unfortunantly limited to 16bit).
Sounds like an interesting tutorial, will have to give it a go.
Hope fully my suggestion is more on the right track 
good luck