For class D airspace, you will have to go through the webpage waiver/authorization process. You can request a certain location with a radius around it that should cover most if not all of a downtown location. Going to take some time. For the class D airspace, does it go to the ground in town? If not, youre good if you stay below the floor. If it does, then you will need the waiver. You can request it for some period of time. My first authorization was for 3 months, then requested a waiver to cover the same area for up to 2 years. Under the terms, I still had to notify the appropriate air traffic control before flying there.