The coticule is a finishing stone and that is what it is best at. In general if you have to do much more than 20 minutes your really spending too much time and a lot of guys will give a razor like 20 strokes or so and that's it. If you need to do like hundreds of strokes you probably should back up to the 8K. There are instances with certain types of razors and steels where you might have to do a lot of honing on the coticule but that's more the exception than the rule.

So if you are doing all these strokes and nothing is happening then either your doing something wrong or your razor is really dull. As far as slurry goes you really should have a slurry stone. If the stone you are using is softer than the coticle your slurry will be from the slurry stone. Usually a slurry stone is a small piece of the same thing as the honing stone. With most stones though as you hone you do develop some slurry as the blade contacts the stone. I have a slurry stone with my coticule but I never use it. Some have said the stone cuts more aggressively with the slurry stone.