Jon,
The paint is spray paint. It usually costs about $5.00 a can and works awesome with the small irregular flecks in it. I also get the stone fleck paint at a home improvement thrift store we have here called Habitat Re-Store. It only costs me $1.20 a can when they have it in stock. I just picked up 6 cans to keep on hand.
Another low cost solution for a similar effect would be to use regular flat cream colored or greyed paint and before the paint dries, throw saw dust on it in an random pattern. Just use a little at a time and build in layers with more spray paint until you get the effect you want.
Crazy, I'm pretty sure they'll post the article on the website in September.
The Dark Tomb - Psychological Terror at it's best!
www.mansionofterror.com/props.htm