Gary,

I presume with 4K and 8K, you're talking about the Norton.
You can go Norton 4K, Blue with slurry, Coticule with water.
You can also go: Norton 4K, Norton 8K, Coticule with water.
I don't know which would be sharper, since I don't own a Norton.

I agree. The Norton 4K, Blue with slurry, Coticlue with water is what I prefer to use. Sometimes I wash the slurry off the blue and do a few more passes before moving on to the coticlue with water but I don't really think that it makes a difference.

Not all razors respond equally well to a given honing method. Sometimes, it comes apparent during the first shave that the razor lacks on the keenness front, although you're positive that you had a perfect, very sharp bevel after the 4K. In such stubborn cases I try the double bevel method.
To do it, add two layers of electrical insulation tape to the spine. Hone 20 extremely light laps on the coticule with water. This creates a nice and clean microbevel at the edge, and a whole new shot at achieving the sharpness you were after in the first place.

I personally don't like to do the double tape method because then I have to match the bevel on later touch ups, but it will work as you said.

best regards,
Bart

Always nice to hear from you Bart