I wouldn't worry about stalling him, we never have. Its been a few years since we had to wean but it seems we did it gradually. Seperated them during the day then back together at night for a week or so before we seperated them for good. We have a dry lot and pasture seperated by the driveway. They could see each other all the way through the weaning process. I don't recall how long we seperated, it seems it was 3-4 months. We would put them back together and if the baby started to attempt to nurse we would seperate them again.
Its good you have another horse to be with your weanling, that always makes it easier.
"Until one has loved an animal, part of one's soul remains unawakened..."
- Anatole France