A few months ago, I managed to get a pair of Soubirac riding boots at an almost unbelievably good price. They turned out to be a model that had been discontinued a couple of years ago, and were badly marked (one marked on the sole as being a size 45, the other 44, but all size markings on the inside match up to being 44).
Brand new, they were bloody tight around the calf and the leather was also quite stiff, marking them very difficult to get on and ridiculously difficult to get off.
So for a few weeks I worked at softening them using neatsfoot oil and another new toy of mine: a hot air gun with controllable temperture.
I blow hot air into the boot at 80°C to start warming it, and paint the outside of the boot with neatsfoot oil. Then dial up to the temperature to about 140°C and warm up the outside, playing the hot air over the surface of the leather. My hand and bare arm inside the boot allow me the feel how warm the leather is getting.
My reasoning is that the heat will drive off some of the humidity that might be still trapped in the leather and that it will also make the oil less viscous so that it soaks into the leather more easily. And it seems to have worked well: the boots are now supple enough around the ankle that I can comfortably walk the 800 yards or so between my house and the stables, ride for a while and walk home again. The longest I've worn them for in one stretch is about six hours. Oh, and I don't need help getting them off, any more. Now, I generally reapply the oil after every two or three hours or riding. The inside of the calf, where it rubs against the horse's flanks, seems to absorb the most oil. The amount that is absorbed seems to be getting less and less, so maybe the leather is reaching saturation...
I've been using the same technique of heating to treat a few of my old leather belts and also some old odd stirrup straps fished out of the rubbish pile at the stables: a broken buckle, perished and broken stitching, dried out leather, all seem to be "good" reasons for chucking out what have turned out to be OK looking straps. I sew on a new buckle and then use the straps for bundling up bits of kit, like a raincoat rolled up behind the saddle or over the pommel when going out on an all-day ride.
But today, looking at a thread on the Horse and Hound forum, I saw some interesting opinions about how to treat leather, especially straps (specifically girth straps, but this would apply to stirrup straps, too). The opinion is that neatsfoot oil should not be used on any strap that takes a heavy load, as the oil loosens and spreads the fibres; this seems logical to me, in that the loosening and spreading effect is what leads to the suppleness.
There are also some interesting ideas about how the leather a century or two ago would have been made from the hides of much older animals than is the case today, and that tanning techniques have also changed, and so many of the "old-time" recipes for leather-dressing compounds would be ill-suited to today's leather.
I scored myself a second-hand saddle a couple of weeks ago, and had already oiled the billets, the insides of the flaps and the gullet once, before reading that Horse and Hound thread. Next job is to make up a pair of stirrup straps, I bought teh buckles and a big piece of butt leather for this a while ago (I'll borrow my daughters stirrup irons). But I'll not be putting neatsfoot oil on the straps!
I know there are a few professional leatherworkers on here, and a number of accomplished hobbyists; what do you think of neatsfoot oi, and what would you suggest using instead?