Let me open this post by paraphrasing and adding to a quote by Aristoteles.
"The more I think I know, the more I know I know nothing". This is so true for me on the topic of honing, particularly honing with naturals.
My best Zulu edges come from an edge that is good after the 16k Shapton glass, then I hit the Zulu with water only (most of the times) or light slury (one or two light figure eight with a well worn dmt325 or an Atoma 1200) then diluting to water in ~60~80 strokes and continue on water only or honing smith solution for another ~80 more strokes on my smooth side of the stone. Some times, if the blade shaved good after the 16k Shapton and paste regiment, I take it to the Zulu on the smooth side of my stone with water first, then honing smith solution. This usually results in a bit more sharpness from the 16k and gain smoothness.
I have two lapped sides to my Zulu. One is finished on the 1200 Atoma, which is quicker and straighter, but as smooth as the well worn DMT325 I used to use. The other is dry sanded (after the finished lapping with the Atoma 1200) with 1500 wet/dry sand paper. Which gives a slicker and shinier surface than the other side (1200) when wet.
I find the edge out of the 16k, very sharp, but a bit harsh. I have achieved outstanding edges from the 16k follow by paste (CrOx and CBN), but find that this also is not always consistent in all the edges I do with this method. IMO the Zulu adds that feel of "natural" where the edge is sharp and smooth to the point that the irritation is very little or non existent on my face. It doesn't add the buttery feel of the turis (the only other naturals finisher I have), but IMHO, as sharp if not sometimes sharper than with the yellow green turi.
Lately (6 month or so) I have been experimenting with going from a good 8k edge to the Zulu. And after several methods, hits and miss, I have settle on the most consistent method for me at this time. Which is, taking the 8k edge to a water only refresh Zulu surface with an Atoma 400 (leaves a "rougher" surface than with the 1200 Atoma). Doing about 60 to 80 laps, then refreshing the surface with an Atoma 1200 and doing another water only 60-80 lapse on that. I rinse as I see swarf/slury (not sure) building in the water (happens more with the 400 surface. Then I go to the smooth side with water or smith honing solution and doing weight of the blade strokes for another 80.
I also like after the stone to do 4-6 strokes (no more than that) on .5 CrOx to really take the edge to the next level. IMO it doesn't distract from the Zulu edge, but enhance it. If I loose sharpness because of the CrOx, then I go back to the "smoother" side of the Zulu and do another 40-60 strokes. This sometimes results in a better edge than I started with, before going to the pastes.
I also feel that I use more "pressure" on the edge that I would on a the 16k Shapton glass or a Turi, at least at the beginning of the honing on the "less smooth" side, and then going weight of the blade as I finish the strokes. It's like I try to slice a very thin piece of the stone, making sure that water pushes all along the edge. If water is not pushing evenly with the little pressure (read "NOT setting bevel" pressure) then I strop, first 7-8 on CrOx then hard wool felt (after rinsing and drying blade between the CrOx and felt) then I try again on the stone.
Like I said, the 16k then Zulu, is my best and most consistent method. If you only have an 8k synthetic or natural (coti), then the three surface approach is my second best. If you don't have a rougher lapping plate than a well worn DMT 325 and or an Atoma 1200, then I would just refresh the surface at least one time in the middle of the honing (a la Hirlau) and/or use slury (always light).
A note on water, I use more water in the "less smooth"/"rougher" surface than I use on the smooth. When I'm finishing the last 20-40 strokes, they are done on a "no poodle" stone. The edge pushes water but I only see it on the very edge, not ahead of the edge like on the Shapton glass, and only weight of the blade. I waited one time for the stone to dry and do another ~10 strokes on a dry stone. The edge was on of the best I had out of an 8k edge.
By no means I think this are the only methods. I have tried pyramid with the Shapton glass 16k and the Zulu (1:20, one stroke on the Shapton to 20 on the Zulu) and that have worked. Also tried CBN spray (light) with water on the Zulu and that worked very well too. One stone method out of the 1k with diluting slurry, and that gave me a smooth shave ready razor but not as sharp as an 8k (if I remember correctly). I read, this one stone method have worked for other, but I think it requires a lot of finesse as to how fast or slow to dilute the slury. One of my favorite edges out of the Zulu, is to use turi slury on the Zulu (again, light) to finished an edge. The turi is "softer" (they are both hard) and gives the slury with ease by just rubbing the turi over the Zulu.
I'm also curious as other peoples method. Reading the posts, it seems most people get the best edge out of a Nani 12k or Shapton glass 16k follow by the Zulu.
Hope this can help someone! Double O