Ghusl of the Deceased
Question :

Is it necessary for a Shia to wash the corpse of a Shia?

Answer :

Yes, it is necessary for the Shia deceased to be given the ghusl by a Shia; if that is not possible and a Muslim that does not follow the path of the Ahlulbayt (peace be upon them) is the only choice, then based on an obligatory precaution he should perform the ghusl himself and then do the ghusl on the deceased.

Ghusl of Decomposed Body
Question :

If a body is decomposed beyond recognition or badly burnt, how can we perform Ghusl on it?

Answer :

If Ghusl cannot be performed or it leads to the dead body breaking up and damaging it, then it is not mandatory. If the dead body has not deteriorated to such a level then Ghusl is mandatory.