I have successfully bred many little jap quails over the years. Here's what I have learnt:
they need to be in an aviary where the birds above aren't destructive of their nesting
they need cover and to feel safe
they need their own food and water
don't mess with them when they start laying, female quails lay many eggs then herd them all together into a safe corner then sit on them, they can lay them all over the aviary then roll them into one corner.
they need small wire to keep the babies in and safe
when the babies hatch they need water with stones in it so the bubs don't drown
they also need egg and biscuit mix (available from pet stores) with some small (finch) seed which the babies can eat, mother quails don't feed their babies they are like chickens the babies are self sufficient as soon as they hatch.
if you are in a cold area where the rain may affect the aviary they are housed in you will need to cover the avairy at night and when it is raining or cold.
they certainly aren't broody things, they are seasonal layers when food is at a plenty and usually when it is warm.
you sure your not talking about king quails? i know a few people that call them japs.
japanese quail are very easy to breeds as long as the have a good high protein feed (25-30% protein) i find that 2-4 females per male works best, if more then one male per pen then 4 females per male. putting new males in a pen that already has males does NOT work, they may fight to the death.
also dont put then on sand, i tried this and i spent a lot of time getting dried poo balls off there feet
they will also lay there eggs anywhere and usually dont use a nest.