I've heard of Mane and Tail, originally for horses. Personally i use Biogroom. You can email them and get free samples. I got four 4oz bottles, and two of them are concentrate (so dilute 4 parts water one part shampoo) I've lasted a long time with those free samples
there are a lot of good products out there, but that's what I use.
When Uni was a baby I bathed her every 2 weeks. She REALLY needed the bath by then. I think as puppies they are more sensitive, so I just beared with it. Now she is going on 3 yrs, and it's about once a week.
Oh also when you bathe, don't use too hot of water, and when you blowdry use warm air, not hot. I even rotate between warm and the cool button. So they don't get dry, tight, itchy skin and scratch.