1. QT
2. Deep, burrow-able substrate. It's been a while since I've kept dumerils, but with my other burrowing snakes I use oak leaf litter. You'd be surprised the difference it makes.
3. Proper temps. He does not need high humidity. If it's at least 40%, he should be fine.
4. Cover the enclosure and put him in an area that receives no traffic.
5. Leave him be for a week. Any interaction should only be done to make sure he has water and his husbandry parameters are correct.
6. Do not feed him for two weeks. After he feeds and poops - have a fecal run.
If during this two week period his health deteriorates, take him to a vet.