depends on the spot really, if it's just a wall on a street probably give it the look left look right then go for it. if its a yard/lay/etc or whatever probably a little prep work for example theres no yard near me but there is a one track runoff ive noticed has had a freight there every once in a while. looked it over on google maps, checked the full train schedule, spent some time just scoping it out and seeing what time workers leave it for the night etc. just need to pop the fence open and itll be ready. might be a little overkill but a spot like that where i live is rare as shit and id rather spend more time prepping = more time painting than running in blindside and getting a 1min throw on it.
but ye all depends on spot/location/what it is/etc