It really depends on how old the horse is how severe the founder is and what caused the founder for one. But a knowledgable farrier can do wonders for him. One thig the farrier can do, is when trimming him to be shoed, the farrier should lower the heel as much as possible to balance the foot and take the weight off the toe, generally where separation starts. Lowering the toe will also put pressure on the deep flexor tendon, with pulls on the coffin bone, and will help reset the coffiing bone in place. The main factor when dealing with a foundered horse is to take the pressure off of the toe where the wall has begun to separate from the sensitive laminae.
As an ower a few rules to follow with a foundered horse is, don't allow them to eat lush grass if they aren't use to it, generally most horse do not need grain, but owners tend to think they do, and don't overwork the horse after they have been freshly trimmed or been off for a long time.
As to the difference in donkey feet as to horse feet. Donkeys and mules tend to have more club type feet then horses, so thhey do need to be treated different.
I wish you good luck with your horse/donkey! :)