I am one to wean slowly, and, having tried just about every way known to man in the last Lord knows how long, I find this works best.
The one thing that stands out form all the different advice you will get, though, is that if you wean at the right time
for the mare and foal as opposed to the time
you think is right, there will be less stress.
I have a colt and a filly who are ready to leave now, and the mares are ready to let them go, both mares are back in foal although they are not "dragged down" (sorry, never had that happen) they are ready for the foals to leave.
Both foals are four months old, and they will stay on another two weeks as I know the mares are not yet "sick" enough of their foals to have them go without stress, and I have to geld the colt. So he will go with Mama to be gelded, stay probably a week longer on the mare, then both foals will just not go out after being fed.
They are in the front stallion paddock to be fed, it is sheep hurdles and they can see the mares, touch noses and talk, just not nurse.
They come in each day, get tied up, handled and fed, and then stay in there for an hour or two.
When the colt is healed they will just not go out again and I do not expect any problems.
Timing, that is the most important thing with weaning, if you get that right everything else will fall into place.
Your foal needs to be eating feed well, and hay, and drinking water properly, BTW, both my coming up for weaning foals are eating a good feed each day, which cuts down considerably on what they take form the mares, and I'm pretty sure this is one of the reasons I never have thin mares.
Quite the opposite, I'm afraid