hatching coturnix for me usually starts early day 16 (although it has started as late as day 18), they tend to come in waves, i get a big hatching all at once then nothing for several (4-8) hours, then a second, and largest, wave comes all within 10-15 min of each other then another pause and the last come sporadically, after the second pause. i usually give them another day before tossing, in the picture above the second wave came yesterday morning, i cleared the hatcher around 5pm of all hatched birds and this morning there are only 3 more that had hatched. i have Marans eggs going in the hatcher after i get back home from taking care of everything at my breeding barn, what doesn't hatch by then will go in the compost.
the only way to know if you have an internal pip is to candle it and/or you can hear the chick chirping. internal pips can be very difficult to see on spotted quail eggs such as coturnix.
i have my brooders already set to the proper temp (100° for quail chicks, 95° for most other fowl) so all i'll need to do is plug them in and let them get to temp and stabilize but i keep a plastic tub in the incubator/hatcher room with a heat lamp, i plug it in about 5 min before moving anything from the hatcher into it, it's lined with paper towels only so there isn't a need to wait for the bedding to get up to temp. my brooder battery (GQF 0540) only takes about 5 min as well to come up to temp and stabilize (i use the DACB paper to line the floor for quail the first 7 days, chickens can go directly on the wire). i have some much larger brooder boxes i built for hatching out large numbers of chickens that i use pine shavings in the bottom of, they require several (4-5) hours to get the bedding up to temp and stabilized.