What are the best ways to stop an asteroid heading for the Earth?

Significant amounts of technology testing would be required for this method to be validated in effectiveness. For instance, the surface properties of the asteroid must be taken into account:

• A dusty surface combined with the impact of the paintballs would reduce the surface % covered by the paint.
• Microgravity (assuming the asteroid mass is small) would inhibit the effectiveness of the paint contact to the surface - reducing the surface % covered by the paint.