It took me a couple tries but once I got the technique down, I won't ever go back to anything else for seed starting. The pH of the water really isn't important at this stage (in my experience), and the idea that you should never let coco dry out is also something you want to ignore until they are established with a solid root system...the cycle of wet to dry to wet again encourages the root growth. I have never had a seed that did not show a tail within a day or two of soaking that was not viable with this seed starting method. The only seeds I have ever seen not pop with this are the ones that probably weren't viable to begin with, but your mileage may vary. Here's the technique I use:
-Soak 24-48 hours (not necessary, but speeds the process along a bit) until you have a 1/4"-1/2" tail
-Tap water, 1/3 strength coco nutes (in my case 5ml each Canna A and Canna B). In my case, tap water and using the coco-specific line of nutrients from Canna at or below the recommended 15ml/gal dilution has always produced excellent results across the ideal range of pH for coco, from the mid to high 5's to the low 6's. YMMV depending on the mineral content of your tapwater, but I do know that Canna and probably other coco nutes as well call for tapwater specifically over R/O.
-For containers, you can go with seedling trays or small plug-sized cups to start out with if you really want, but I recommend you just cut to the chase and start them in the initial container (for me, this would be a 4" pot until the first transplant)
-What you want to do is run enough of the nutrient/water solution through the coco to get a considerable amount of runoff, maybe up to 100-200% runoff, and then squeeze it until it is about as dry as you can get it by hand. Couple different ways to do this: for smaller amounts of coco, an old pillow case works wonderfully as a "strainer" and then you can squeeze it to get the water out. If you're planting a ton, or transplanting into larger pots (this works brilliantly for that as well, same exact process) and need to do a bigger batch at once, go spend $5-8 at your local Wally World for either a very fine mesh or cloth laundry bag and use it the same way as the pillow case. Either way, you want the coco to be just moist enough to feel it, but not so wet that it leaves water on your fingers.
-Plant as per usual, keep the humidity at a nice comfortable level for seedlings/vegging plants/humans (50-70% is fine), and don't even worry about humidity domes or anything as they aren't necessary.
-If all went well, you will see seeds breaking surface within 24-36 hours, maybe 2 days at most.
That's it. I don't mean to oversell it here, but this technique has saved me so much heartburn and so many hundreds of dollars in seeds since I learned it that I can't help it.
One caveat here -- I have not tried this without nutrients, as the conventional wisdom of coco is that you never water without feeding at the same time, but I suspect that you can get by just fine with regular non-phed tap water until the cotyledon starts to yellow. If transplanting, I would probably guess that you want to at least do the 1/3 strength nutes as described above. When in doubt, less is more, so feeding on the lighter side is usually a good bet regardless of what stage you're at with coco.
I'll definitely use the protein scoop dome thing next time for sure!