Who do u ask for a legal wall!!!! I tolled my parents i was doing legal grafiti but i dont i bomb i at least have to do 1 legal so they believe but who do u ask at the store the manager or wat and can u do it over the phone????
Try a small business thats seems "creative". Ask the owner,say Ill paint you a mural for free,if you dont like it ill paint it over with white again....make sense?
Just go to whoever's wall you want to paint on and tell them openly that you'll paint their wall for free and if they don't like it you'll do it over. Going in person is probably best but doing it over the phone could work too. (It's best if the owner/manager sees your face)