For some reason, people seem to think that frequent baths are not good for dogs. Perhaps some poor animal who got washed with laundry detergent and cold water from a hose started the rumor...who knows?
In any event, bathing is a good thing. And yes, you can do it once a week. I certainly do...even though my boys are not too happy with me at bath time, it is a different story when they're nice and clean. Their whole attitude changes...they are happier, livelier and far more rambuncious.
Always use a shampoo formulated for dogs, however, pay attention after the bath to their reaction. Our oldest dog has always had sensitive skin. After experimenting with a few shampoos, I ended up going back to puppy shampoo which helped a lot. However, my best find, and the shampoo I'm using now, is an Oatmeal shampoo (with some Awapuhi moistuizer thrown in for good measure!). Sometimes it's a bit of hit and miss, but you will find a shampoo that works with your dog.
Use lukewarm water, being careful not to get shampoo in the eyes or excess moisture in their ears (as this can cause ear infections). If you do get water in their ears, dry them with the towel or some cotton swabs.
Frequent bathing can also help you diagnose any potential health problems. If you bathe your dog regularly and he or she still has dry, flaky skin or continues to smell bad, then you know to take your dog to the vet for treatment.