I am the one who had a foal take three days to nurse from Mama.
Obviously, as with Susanne, I was bottle feeding.
My foal would actually turn his head away from the mare and actively avoid nursing.
I had a mare who has now stopped breeding , ALL her colts did this!!!
It made for an interesting first two or three days!!!
Basically just keep on as you are, milking the mare off and feeding, and half way through the feed stop - the foal will get annoyed at this and so be motivated- and "plug" the foal on the bag.
I tied the mare up and literally held the foal and placed his head on the bag, slipped my thumb inside his mouth and milked the mare into his throat.
Since he would not suck standing up , his first real meal from Mama was taken sitting in my lap with his head vertical above me and held in place by my hand- a technique I perfected with the other mares foals.
Once the foal has actually made an attempt to suckle- in any position- it has found the breakfast bar.
It is not necessary to hold the bottle by the bag etc as foals have a keen sense of smell and will search for food.
My problem was that my last foal with this problem was extremely premature and he was a full three days old before he was strong enough to allow him to get hungry.
This occurred naturally in all the cases I have had as I became so tired I slept through a feeding in the night!!
Once the foal has become hungry- so long as it is strong enough- it will search on it's own.
If you are in the stall- leave as the foal will now associate you with food and will search all over you- which is confusing!!
Just go outside and watch.
In all my cases after I had missed or was late with a couple of feedings the foal took less or no milk from the bottle, indication to me that it had nursed.
I cut back on the feedings- only offering a bottle a very two hours and within 24 hours all my foals were nursing normally and refusing a bottle.
I think I have had five of these, counting the very first over 12 years ago.