How to get the smell out of my van?

When I bought my van, it was sitting in a barn for 10 years, filled with mice droppings and pee. We stripped it and got that smell out but hosing it out and spraying it with various chemicals. After that, it got a mildewy smell, we assumed because of standing water, and it was so we drilled hols to let the Water get out. It didn't smell too bad after that, it still had a faint smell so we poured baking soda in it and left half a box in there to absorb the smell. Now, it smells like really old, stale crackers or something. It's not bad, and its not the greatest. We were going to paint it with Kilz, to make the inside look better, but to get rid of smell as well, should we do that now, or completely knock out the smell first? If we should completely knock it out, how so?