Mildew can linger even after the best of clean-ups.
You didn't mention the l x w x h of the crawlspace, whether it's a poured or dirt floor, or what its specific venting is (if any). You want to tell us what the crawlspace was like BEFORE this flood. Was it dry all the time? Did it get wet a little during light or HEAVY rain? And before you do too much, you want to make sure your gutters are sound, that they're free and clear of debis, and that the downspouts are carrying water at least 3' from the foundation. Hopefully, you have a slope of at least 1/4" per foot away from the foundation, and that water doesn't end up back at the foundation after it comes out the downspout. You can improve ventilation and reduce moisture entering the crawlspace, but if you have a few minutes, reply with a few more specifics and I'll be glad to help.