I wean by taking one mare out of the field at a time. It'll usually be a mother of one of the older babies, or one who's bringing his dam down. Most of mine don't even notice that they don't have their mom there. We have been weaning at the end of July, but this year we are gonna wait til mid August.
Most guys around here just run all their mares in one day, put the babies in one pen and either the mares go back out to the field, or get put in separate pens. There are a lot of PMU farms around here. I joke about doing it like that, but I never will. By the time my babies are fully weaned, they are used to be away from mom for small periods of time. We ride most of our mares, so we'll go for an hour or so now and then as they get older. When mine go to new homes, they are weaned, halter broke and can generally be bathed and clipped. And I train them to load before they get picked up. I've bought several who had never been here a trailer before we picked them up. It so traumatic for them.