DMT Continuous Diamond Coarse... hands down!
You could use the holy DMT stone but I don't know why you would as you get LOTS more diamonds on the continuous diamond stone. I haven't calculated the total surface area of the holes but if one took the diameter of the hole, halved it to get the radius, squared that number and multiplied by 3.14159, you'd get a number equal to the surface area of a standard hole which you could then multiply by the number of holes in the surface (you count 'em). Subtract that total from from the 24 sq. inches of a continuous diamond stone and you'd see the amount of diamond surface you're losing by going to a holy stone.
I have very rarely needed to lap a stone on an XX DMT and I've bought some really dished out stones! It certainly wouldn't be necessary for a coticule maintained in reasonable condition with a DMT 8" coarse continuous. I do own and XX DMT stones for the very good reason that I sharpen lots of stuff and they really eat steel quickly. The other reason is that end of the diamond stone market isn't stable. 3M pulled out of that end of the market and don't make them due to lack of demand. At one point in 2006 I had to order a run of XX stones in order to get any as DMT wasn't selling a lot of them either. The DMT stones are such excellent tools I did buy the whole run as I didn't want to get caught without the ability to own one.
If you're going to continue playing with honing and with stones, you'll probably end up with a full range of those stones. They seem to last a really long time and don't dish. I've been using the same stone to lap coticules before I ship for the last five years and that stone is still looking fine (DMT 8 Coarse). Just rinse and dry after use and you'll have a quality tool for the rest of your life.
One indicator I get from my "extreme customers" who usually live way away from urban centers in places like Australia or New Zealand is that they order the full range of stones in one go and then are set for life. They get the XX, X, E, EF, the blue belgian and the coticule. I've gotten that kind of order several times and when I ask them what they're sharpening they say everything from razors to knives, machetes, fine cutlery, fishing spears, etc. When you're living back of beyond, you live by your edges and they need to be sharp or it just increases the effort you have to put out to get by.
Howard