The rough side of a piece of tile or a small terra cotta pot works best. But if you change the environment too suddenly, it may throw their cycle of for a little while. As for time cycle it depends on tank, temp, water etc. Mine take 8 days. A good rule of thumb is when the eyes of the fry turn silver hatch night is close by. Typically 7 to 10 days. If you can pull them with a few gallons of water on hatch day or close to it, I will have a 5 gal tank ready. They need to stay with tank water for the first few days. And If they are still eggs, need a very slow bubble of air to keep them aerated but the dad clown does a better job than an airline can. So the longer with the parents the better.
I can't pull the rock that my eggs are on out. So I have to wait till hatch night. Shut all pumps, power heads, etc off and run an airline. I cover the tank with a few towels to black it out at lights off and wait a few hours. Then I start the painstaking process of siphoning the fry out with a small section of airline( the shorter the better) they aren't a fan of long journeys.
Let me know if you need any help. Where are you located?
It's more than luck - I tried my hand at raising blue dempsey fry once and it was rough. I think several times I lost all the little boogers and couldn't figure out why. I did have a couple successful batches, but it was depressing watching them grow and then for seemingly no reason (although undoubtedly there was one), I would come home and they were all dead. It is very time consuming and you have to sort of be on top of it at all times. Can't wait to see more pics of the babies!