These dogs don't require bathing often. "Do Bernese Mountain Dogs smell?" is a frequent question from potential owners. The answer: not as much as you'd think! Unless they roll in something stinky, these dogs usually only get the well-known "doggy odor" if they get wet often and dry naturally. So bathing a BMD is typically at the owner's discretion.
To bathe your Berner: make sure to give the dog a thorough brushing first. Your best bet is to use an outdoor kiddie pool and a garden hose, but if you must be indoors, a walk-in shower works. Also be sure to use canine shampoo, as the kind made for humans will irritate your BMD's skin; owners say a canine shampoo with oatmeal works very well on these dogs. First wet the coat thoroughly, then apply a silver dollar-sized amount of shampoo to the dog's back. Lather well, working downward and outward as you go. Make sure you lather the belly, insides of the legs, and tail as well; finish with the chest and neck, then use a washcloth to clean the head, ears, and face.
Once you're done with that, rinse thoroughly. (And with the Berner's thick coat, rinsing all the shampoo may take a while!) Once the water runs clear through the dog's coat, squeeze any excess water out with your hands, then towel- or blow-dry (or both); just make sure the coat is as dry as possible, or you run the risk of it developing the dreaded "doggy odor."
Finish with another quick brush-through to make the coat look fluffy and clean.