Yes, food is the way to go. There are a couple of strays I feed that was initially very unfriendly and frightened, ET was one of them. I won't go very near, but will leave food at a distance and within their sight, so they know there's food, then leave. You just need a few days before they know they will get constant food source at the same spot. To gain trust, it will depend on the cat itself, some slower, some faster. I'm still feeding a black cat that will still stay a distance from me, though she is getting closer and closer to me now and its been more than 2mths. It took ET just 1 day to know he is getting food at a specific place. Fed him once, he waited at the same spot the following day and the days after. He will usually wait at a distance for me to leave food there and waited till I leave before he came forward to eat. It took him some 2 or 3mths before he came forward to brush me.
If you know there are cats hanging at a specific location, you can always leave food nearby everyday. When cats know there are food all the time at the same spot, they will come.