It is a bit tricky, to be sure. An export bus set to export endstone only by crafting it will only put 1 into the target inventory every time it crafts them, so the extra end stone piles up in the network. The export single/craft option will send all the endstone you have before trying to craft, so you won't have the 1 end stone you need to craft. I think the best answer is export redstone to a fabricator set to that recipe, and import endstone from the fabricator. Stick an inventory with 1 endstone next to the fabricator so it can always craft, and set a level emitter next to the redstone export bus to stop it when you have say 2 stacks of end stone (don't use stack mode, just export 1 redstone at a time).
EDIT: never mind. The fabricator removes the end stone from the adjacent inventory when it wants to craft. Hmm...
Instead of the import bus, use a storage bus configured to store end stone in the fabricator, so it will stay there but be accessible to be exported to macerators/pulverizers. Then all you need to worry about is running out of redstone or exporting the endstone so fast it doesn't get replenished.