I recently crashed in a dune.I replaced the propellers, remove the sand from the motors with an air blower (and a lot of patience) and the drone is flying fine.

Now that I'm at home I want to properly clean it. What are the best practices?
contact cleaner in the motors? Isopropyl alcohol in the outside?

Hi, there. We are sorry to know about this issue you've encountered on your device. If the device has experienced an accident, we suggest sending it to our facility for a proper diagnosis. This will also help us to ensure the future flight performance of the device, as it will undergo flight tests and quality assurance. You can contact our relevant team through this link: https://www.dji.com/support for further assistance at the request to start a case and investigation on the said incident. Thank you.