I have two boxers, one all white. I only bathe them about once a month. We go to the park every day for romping and wrestling around in the mud. Luckily, boxers are short haired and have little if any undercoat. So, many times, the dogs will look really muddy, but by the time we've walked home, they have shaken most of the dirt off themselves. What is left, I usually take a damp washcloth, and wipe them down. When their fur is dry (doesn't take long at all with short hair), I take a rubber brush, called a curry brush, and brush off the remaining dried dirt.
And like was said above, boxers are very clean dogs. Mine wash themselves a lot and wash each other as well.
Boxers tend to have dry skin so frequent bathing can cause some skin irritations and itching, and other skin problems. If you need to bathe your dog frequently due to rolling in poop (as mine seem to do every couple of weeks), I suggest a very mild, oatmeal enhanced soap. I use puppy shampoo on my dogs and it works very well, without drying their skin. I do use a special shampoo for Susie for white coats, which cuts the "yellow" tinge some white fur dogs can have.