We've used the typical cushion overboard for drills, but I've found that isn't all that realistic, since the cushion tends to drift with the wind far faster than a person would. A weighted or drogue equipped buoy would probably make a much better MOB target.
In sheltered waters, during the summer, I've done MOB drills with crew who wanted to go swimming.
I've also had them practice with the LifeSling2, which I think is one of the better pieces of MOB recovery gear a boat can mount.
Getting an MOB back on board seems to be the hardest part of any MOB recovery. On my boat it isn't that difficult, especially with the use of the LifeSling, since there isn't much freeboard on the amas, and hauling someone up onto the ama deck is reasonably easy to do. Of course, on a monohull, the freeboard is going to be much more of an issue.
Generally, I'll approach the person in the water and try to leave the boat upwind of them, and let it blow down to them. The amas have so little freeboard, that they can easily grab onto the boat. Also, the boat, being a trimaran, tends to be affected more by the wind than the person in the water is, so having the boat downwind of them, makes it very difficult for them to catch up to the boat. The upwind approach also puts them in the sheltered side of the boat, which helps out a lot.
I haven't tried this in heavier conditions, but I do see some problems that might occur in heavier seas, due to the motion of the boat.