Thank you! High praise indeed.
>> my DH does not have the patience to drip water into every little cell.
It was super-easy to "water the mat, and the mat will water the cells".
I would test it for a week or two before leaving it to a non-gardener.
You could even leave one central cell empty of mix, so he can pour a measured amount of water right into that cell. You could measure how much water is needed to bring a dry mat or mostly-dry-mat up to water-logged or very slightly awash.
I think the key thing is that every cell has to have a drain hole where the mix can TOUCH the fuzzy mat.
It did WORK for me using the skinny-slit that was "burned" or melted into the cheap 72-cell inserts, but I didn't trust it as much as I trusted plug trays that had big honking HOLES. If I was watering Dixie and Solo cups this way I would drill 1-2 1/4" holes on the bottom.
(Maybe add a few small slits or small holes on the side, for letting air exchange without having to diffuse through a damp cap mat. I did not do that either of my first two years starting seeds this way, and they seemed OK. Perhaps because I have such a coarse mix that air can diffuse all the way down from the surface. But next I plan to try some very deep 50-cell plug trays, and maybe a mix that does not drain QUITE so fast, Maybe a deep cell with a fine mix will benefit from air holes on the sides.)
I do think that almost any mix with any peat will wick well enough, since I had a very coarse mix that wasn't very water-absorbent (lots of small bark nuggets).
