My own experience with bone spur were taking a supplements of magnesium bicarbonate (magnesium carbonate in carbonated water) taken internally or magnesium supplements at 250 mg a day for 5 days out a week for a month, and some boron supplements also helpful.
I think foot soaking in borax solution may work better. Perhaps the reason why the cold water remedy works (my wild guess) is that cold tap water is high in chlorinated water and it makes for absorption of chlorine through the skin better, causing the bone spurs to reduce since chlorine kills off the mycobacterium in the bone spurs through transdermal absorption of chlorinated water compound. Most U.S. waters are chlorinated. A hot water would drive out most of the chlorine and hence less effective.
On the other hand adding a small amount of chlorox as a foot soak might do the same if the chlorinated water are insufficient.
I would much prefer to do a foot soak using a weak solution of Bo Peep (ammonia cleaning solution) plus some borax as a foot soak since both the ammonia and borax are some of the most strongest antifungal or anti-mycobacterium necessary to cause the mycobacterium to be killed or reduce.