Ferrets are fastidiously clean animals. Unfortunately, that has no bearing on their love of bathing. Few ever take kindly to enjoy a bath. When your ferret needs a bath is totally dependent on you and your ferret. In other words, everyone is different. Do not bathe your ferret more than once a week. Excess bathing will strip the skin and fur of its essential oils leading to dry and itchy condition.
If you live in a cold climate you may need to give baths less often. Use a conditioner that is made for kittens/cats or ferrets to prevent skin and coat dryness. If you have more than one ferret, make it easy on yourself. Bathe them one at a time, especially if you have kits.
You will need kitten/cat or ferret shampoo; Q-tips; a warm towel, and professional veterinary ear cleaner.
Have everything ready before you bring your ferret to the basin. This should include filling the basin with 2-3 inches of lukewarm water because ferret do not like the sound of the faucet. Not too much water, you do not want to drown the little munchkin. Hold your ferret gently and securely as you slowly put it into water. If your ferret is frightened, you may want to try speaking to it in a gentle tone of voice.
Begin by soaking your ferret. Then lather it up starting at the head, working your way down through the tail. Be careful not to get soap or water up its nose, in its eyes or too much in the ears. Some ferrets will like the taste of shampoo, don't let them eat any they may get sick.
Moisten a Q-tip with ear cleanser and carefully clean each ear. Do not go into the ear canal. Rinse by running clean warm water over the ferret. Then you should gently squeeze the excess water from its fur and tail.
The ferret should be placed in a warm dry area when you have finished. Give you little character a new, dry towel and watch it play. Ferrets get pretty frisky after a bath! Do not return the ferret to its cage until it is completely dry.
If you find a slight musky odor offensive, you might consider purchasing a portable air cleaner. It will remove odors, pollen, dust mites, allergens, dander, mold spores, fumes, etc. from the air. You can also install an air filter/cleaner (permanent filter that fits into the heating/cooling system in place of regular filter).
There are other things you can do such as removing carpeting from ferret areas and using pure, natural odor-eliminating air fragrances. You might want to go to pet shows and inquire about the unique alternatives in odor control.