My dog is still chewing rocks and swallowing them and the only solution, in this area, is a water-resistant spray. Any ideas? I have read about bitter apple and tabasco, but I need to devise something that kind of sticks, so it doesn't get washed off. I'm going to spray any rocks he brings up to the house, and also try and do large areas of rock and gravel outside. But I need to figure out what to put in it, if anyone has any suggestions?