Most dogs need very little washing, with the exception of dogs with active skin disease (as they accumulate oils and are more predisposed to secondary infections and so need a wash to keep this under control).
Generally you shouldn't wash your dog more than once a week or you can strip oils from the coat and give them dry flakey skin, which in turn can be itchy to them.
In summer, washing is easy as they can go nuts outside and dry off. In winter here, it's harder as it's often bitterly cold, and especially for those dogs with a thick undercoat they can take ages to dry. Hypothermia can be a real risk at times. So if you absolutely NEED to wash your dog on a cold day, you will need to dry them as thoroughly as you can, and provide a sheltered space for them until they are completely dry, or use a coat, or allow them inside.
As for shampoos? If you dog isn't in need of a medicated one, a gentle oatmeal shampoo is all you need. And if you like them to be silky smooth to pat, you can do a conditioning rinse as well.