The most common cleaning method is a mix of 1 quart 3% hydrogen peroxide, 1/2 cup baking soda (not powder) and 1 teaspoon or so of a liquid dish detergent.
In a pinch you can use white vinegar instead of the hydrogen peroxide.
Depending on the size of your dog you may need to double or triple the mix. Maintain the same ratios.
Use rubber gloves.
Thoroughly wet your dog then apply the mixture and leave it on about 5 minutes. No more than that as it can bleach the fur and some dogs are sensitive to it. 
Rinse thoroughly.
Repeat if necessary. 
This mixture should be used extremely carefully on the face because you don’t want to accidentally get hydrogen peroxide in the dog’s eyes.
You can also use a plain baking soda based toothpaste around the face as it doesn't run like a shampoo does. (thanks to a registered vet tech for this tip).
Once the dog is rinsed well shampoo again but with his regular shampoo.
Take the collar, leash and your clothes and wash immediately. 
DO NOT store the mixture for another time. Discard whatever remaining liquid you might have. It can explode if left in a sealed container.
Cross your fingers it only happens once 🙂