No worries, I'm a volunteer firefighter! :-)
Seriously, I flushed with compressed air, then filled it full of water. No propane left, no problem. I cut a hole on the side near the bottom with a torch, then welded a 3/4" union nut on the tank. This let me make a manifold out of PVC that I can stick in the side and get out to clean.
After running it with bleach and then laundry soap then flushing it, it seems ok smell wise. I filled it 3/4 of the way with sand, then flushed it a bunch, circulated water between it and a 5 gallong bucket until it started to clear up. Then I tossed it in the hot tub and an hour later it looks like it's cleaning up the water! And no bad smell so far! One dirt cheap sand filter!
Jonathan