Ghusl of body burned to bones

Assalam alaikum. My question is how the entire funeral ritual of a muslim will be carried out 1) if his body is found to be burned to bones. That is his only remains are bones. 2) if only ashes are available with little bit of evidence that body belongs to exact person Assume police investigated and found 100% that burned body is exact the same missing person or person of interest through DNA test or other evidence.