Thank you, zaapoole! I've studied that helpful post in and out.
I might have been too quick to assist, don't know. After 26 hours after noticing the pipping, my husband carefully peeled some shell. The membranes underneath were completely dry. We moistened them and put it back under mama hen.
2 hours later there was no progress, but the hen had got up, and the egg was pip/zip down. I peeled off a little bit more and noticed the chick had not pipped into the aircell at all. Anyway, if i had an incubator, i would have put the egg in there to keep it moist. Since i didn't, i carefully zipped the egg. All the yolk was absorbed, but there was a tiny bit of umbilical cord on its belly. The chick was extremely weak and sleepy. I was worried that i should not have assisted.
It got better off the course of the day and is happily walking around, eating, drinking, and chirping with the other chicks a day later.
The left chick in the picture is another one hatched today within 4 hours or less since i noticed a tiny crack in the egg. The right one is the one i assisted yesterday.
(I just realized i can't post pictures from a phone, so I'll have to add the picture later)