The easiest way to sex Corydoras is to view them from the top,the females are generally larger and broader,more rounded in general.
I have five Pandas that breed regualarly.
Good feeding,ie live if possible to condition them, gradually lower the water level and allow filter to slow down,I find foam air driven are best,the fry cannot get sucked in and they also feed on the microorganisms present, this also increases the water temp slightly, I also cut back on the food at this stage,then perform 25% water change using water at a lower temp,I usually keep mine at 80f,and use water at 75f to stimulate breeding.
They will usually lay eggs within 24 hours.
Remove the parents and add small amount of meth blue and let nature take its course. 8)