Nonetheless an ash can still make a good blaze tree with a moment's preparation. Glancing blows up and down the trunk with the hatchet can lay smooth a patch of bark for the blaze, down to a smoother underlying layer. This, too, sucks up a lot of paint, but nowhere near as badly as the white oak. And once you've established that smoother spot on the trunk, it will remain a viable blaze spot for years, with subsequent paint coats staying well. Don't come off well with the hatchet, either.
Slippery elm is indeed just that.
All species of hickory are good blaze trees, featuring hard smooth bark held tight to the trunk. Even shagbark hickory, which looks as it might peel off in mighty strips, keeps its bark for years. I have taken to carrying a dry rag tucked into my tool belt for wiping down young maples. You'll see the difference once you've given it a few scrubs. A mowed path helps immensely to define the route, even in the winter until the snow gets deeper than the unmowed vegetation, but we can't get a mower in to every spot.