First, I have never weaned a horse, everything following is from me discussing it with professionals and some general research and my thoughts following it. I think the way you are describing for weaning is one of the best, studies have shown foals that spend the first week of weaning next to their mom (separated by fence) have considerably less stress. Make sure your weanling cant nurse, over or through the fence, if he can, place hot wires on top/in between the rails or install no climb fence in between the rails. Once they seem more independent from each other they can be separated.
“Good things come to those who wait… greater things come to those who get off their ass and do anything to make it happen.” - Unknown