If you have decent light, then put some floating stem plants (moneywort or anacharis can be gotten cheaply) on the surface that can act as a safe haven for the fry. I don't "breed" per se, but I sometimes have Platy/ Molly fry that hide in the plants I have floating on tip of my community tank. I capture them from the surface with a small bowl and put them in a 15 gal I have in my kitchen that's only for fry.
I'll admit this way is dangerous for the fry at first, but if they make it to the top of the water then I can save them. I may not know how many babies were born, but I usually grab 15-20 fry every 6 weeks it seems. This way I don't have to stress the mother out too much (I should mention that my Molly females are significantly larger than the makes so when they are bothered they keep the males in check). Also its cheaper than having a separate tank for breeding, so i let nature take it's course. Here are some pictures of the floating monetary I have and my fry tank!