When I got Freda (as a foster dog) her coat was matted and very long. She had obviously been neglected and, so as not to frighten her, I used to gently comb out the tangles when she was cuddled up on my lap in the evenings. As she came to trust me, I managed to bathe her then clipped her coat fairly short. It has now grown really wavy and pretty, and a beautiful gleaming black.
I was told to keep the fur on her legs quite short so as not to collect mud and I find that works really well. (It is quite muddy here in South Wales!) It makes it so much easier to dry her off when we come home from our walks too.
I don't bath my dogs too often as it can dry out their skin. If they get very dirty, I just shower them down with warm water and only shampoo them if they are very smelly!