How do you get spilled coffee out of a mattress?

I have a new Tempurpedic mattress and I spilled a 12 oz cup of coffee on it. I already took off the mattress cover and washed that on gentle in the machine, but how do I get the smell out of the mattress itself? The company suggested arm and hammer baking soda. Is that the best way? Do I put it straight or dilute it?