Benno...get more females, they are not monogomous like our oscies and don't be dissapointed if it does not go according to plan...I have been breeding guppies for longer than I have been breeding Oscars and I have had alot more sucess with the Oscars. Guppies are live bearers and the adults eat the babies right away. You can put them into breader nets when the females gravid spot is really dark but if you put her in too early and she gets spooked she can deliver premmys who either wont survive or are so small they go out of the breeder net and their dad eats them..also they can always swim back up the breeder net to mum...who will eat them. I have a tank set up with a sponge filter and heaps of silk plants on the bottom for the babies to hide in when they are born. I average around 2 or 3 survivors from each batch, but I get a batch from each female every month, so my numbers are steadily climbing, but even so, if I put them all in with my big O's, a years worth of breeding would be gone in a day!
Go back and get some more females who have fat bellies with really dark spots near their little poo holes - that is the gravid spot - the uterus, and the fatter and darker the closer to delivering - so if you are smart you can buy many fish for the price of one!!
Good Luck!