Learning the correct breathing techniques maintains breath control while walking. So inhaling and exhaling have to be smooth. You can pause your walk for a while and then continue.
If you have difficulty breathing or get short of breath with brisk walking, it is advisable to consult your pulmonologist or cardiologist as there may be some underlying health issue.
I use a technique called controlled breathing to extract maximum performance, it is very simple just like in meditation one must find a rhythm and stick to it.