When horses have been standing in moisture and you scrap a hoof pick over their frog it will have a white substance show up because you are just scraping away the dirt. As for hoof trimming, I would not recommend doing it yourself. There's an old saying of "No hoof, no horse." which basically means if you screw something up you could cause serious lifelong problems. As for the teeth, if he is dropping a lot of his grain, he probably needs to have his teeth floated. Ours are done once a year and you have to have them done by a vet or equine dentist. Hope this helps.