Well, just to throw it out there- wire floors causing sore hocks is a myth. So if your question is based on that fact, I'm about to throw it away. lol
Sore hocks can be caused by a variety of factors, but most commonly, it is caused by genetics. This is not to say that some rabbits are genetically programmed to develop sore hocks, but genetics does affect the conformation of the body and feet. Some breeds, rex breeds in particular, are known for having very thin, small feet, which are very lightly furred. This, combined with their larger body size put uneven pressure on their feet. This can cause sores to develop in certain areas on the foot.
Not ALL rex rabbits will develop sore hocks based on that, though. And sometimes other breeds will develop it for the same reasons. Generally, rabbits with a proportional foot to body size and well-furred feet will not develop sore hocks, regardless of their flooring. Whereas, a rabbit with uneven weight distribution can develop it even on soft, solid flooring.
There are other things that can also contribute to sore hocks. Dirty litter than is not cleaned regularly can cause sores on the feet, or even urine burn in more severe cases. Sore hocks can also develop in rabbits who are housed in a very wet environment, like if they are kept in a pen outside on wet grass during the spring.
In short, a lot of things can contribute. In this case, it sounds like your rabbit just has a body type that favors development of sore hocks. You can treat it with preparation H on the foot until healed. This dries it quickly and it heals pretty fast. The best way to prevent sore hocks in a rabbit who is already prone to it is to be proactive, not reactive. Check the feet daily. Treat them until they are healed, and then treat them again at any time that early development of sores starts. Eventually, if you keep on the treatment, the rabbit should develop calluses and will not need daily treatment anymore. Varying flooring surfaces can also help. Maybe give him a choice of carpet, lionleum, or a box full of shredded paper or pine shavings to relax in. The rabbit will most likely pick the flooring that is most comfortable to him.
Good luck with the healing, and I hope this helps!