Update: Experienced feral cat caretaker writes this:
No, no, no to an absolute dry kibble diet for ferals. That's a lazy mans' way. It's time consuming, but what I do is prepare my feeders as much as I can ahead of time. All feeders have wet food layering the bottom and then covered with dry. They don't get any less than what I give to the darlings inside my home. I don't see them as "less than". They are equals. I make no less than 4 visits to my colonies per day. Early morns are the big feed fest, late morn is checking water supply and taking up leftover food, early afternoon is "snack" feeders put down, and late afternoon is taking up feeders and replenishing water. Because it's scorching hot in summer here, fresh water is a must. I'm especially vigilent during these months.
If the person can supervise the feeding then wet could be put down but it needs to be taken up quite soon afterwards depending on the ambient temperature. It goes off rapidly in warm weather in my experience. I can remember Martha Kane's husband, Richard Vella, feeding feral cat colonies in Malta with dry cat food. Here is the video:
When feeding with dry food, fresh water should also be put down. There should always be a supply of fresh water - common sense.
Feeding early in the morning would seem to make sense. Feral cats feed throughout the day. Evening and morning are probably favorite times as they coincide with their hunting activities.
One cup of dry cat food per cat per day would appear to be sufficient. If there is food left over it is probably too much and vice versa.
Dee an experienced cat lover may like to add to this in a comment.