"What happened to the plan to spray paint them?"
The main problem with painting asteroids, and with similar schemes involving covering them in foil or similar, is that it requires actually carrying stuff to the asteroid. And by far the biggest problem with space travel in general is that stuff is heavy and expensive to carry anywhere. A ground-based laser, or ever an orbital one, would likely be much cheaper - you can build a pretty decent laser for the hundred million or so it would cost for just a single launch with maybe a few tons of paint. Plus, a laser is reusable, and could be used for things like de-orbiting debris when not shooting asteroids.
The biggest problem is, as usual, likely to be political. Giant space lasers are always going to have people suspicious of them, while a big bucket of paint probably won't.