Hola amigos;
To play devil's advocate, because I do not believe the Holmes manuscript is accurate, but just to present the argument in favor that has not been posted.
Yes obviously Waltz would have wanted to help out Julia Thomas, and by extension, young Reiney, for the kindness they had shown him in his last days. However, it could be said that Waltz may well have felt that he had repaid their kindness in full. Maybe even with interest. He had dug up and sold his own 'retirement fund' of gold that had been buried at his home, which was likely the remaining contents from the small cache. The amount of cash this amounted to has been debated but it was a sizable sum. He may well have thought that he had helped them out enough. Also, we have it from some sources that Reiney was not exactly nice to Waltz, even perhaps ignored him when he was trying to tell him how to get to the mine. If this were the scenario, it makes sense that he recognized in Dick Holmes a man that might well be able to find his mine, if given directions how to find it, and perhaps expected Holmes to "do right" by Julia, as well as Waltz's sister which so far I have never seen any documentary proof of this sister. As Greg pointed out however being female her married name would certainly be different, and thus much more difficult to track down at this distance.
Having said this - I don't think the Holmes manuscript is telling the whole story even if it is true or written in the belief that it was truth. Again relying on Greg Davis but have seen it myself, Holmes had some other bits of information obtained in that deathbed interview, that he seems to have regarded as nonsense and disregarded. Those bits of information that seemed senseless may well have been key to locating the mine and cache.
In answer to Greg's question, I think those directions to First Water and Second Water are referring to the same places we know today, as a definite route to the mine, perhaps the easiest route in Waltz's opinion. It is also entirely possible that it is a complete red herring, intended to mislead Holmes OR possibly intended by Holmes or whomever really wrote that manuscript, to mislead any competition to Holmes!
Please do continue,
Oroblanco