How can I potty train 4 dogs???

I've had 2 of my dogs for over 2 years now, actually since they're puppies and they are already potty trained. I just got a 3 year old Yorkie mix and a 5 month old puppy that I found and finally decided to keep. The Yorkie is the only male and drives me crazy cause he pees all over my house and I just run around and try to clean after him. I know that he wants to mark his territory but this starts getting stressful and unfortunately I never catch him in the act...the puppy is getting better and she seems to learn fast. After every meal I take all of them outside in the backyard and go "peepee, potty-potty". As soon as they do what they are supposed to do I praise them. Sometimes they go and sometimes I stand out there for about 20 minutes! Then I get tired and go inside. As soon as that happens they all go all over the place - in the house, the front yard or the driveway. But not really in the backyard where I want them to go. How can I make all of them go to the same place??? ANY IDEAS?