Brothers and Sisters can volunteer for multiple things
Washing & Shrouding of an actual deceased
(With the permission of the Deceased’s relatives)
Many brothers and sisters wish to volunteer after hearing about the rewards involved with washing the deceased body of their fellow Muslim brothers or sisters.
Although machines can intervene to bury our deceased Muslims, it is the Sunnah for Muslim men to be in charge of lowering the deceased into the grave, facing the Qiblah, and dirt placed over them. At times, there aren’t enough at the Janazah Prayer to physically lower the deceased Muslim into his grave.
Attending Salaatul Janazah (The Funeral Prayer)
As we know, offering Salaatul Janazah on our deceased Muslims is Fard Al Kifayah- (a communal obligation, that if some fulfil, they suffice for the community, and if none step forward, the entire community is at sin.) Now many of times there are no followers to the prayer or to the cemetery except a few. Rasool Allah ﷺ taught us that as the number of people in the prayer increases, it is better and more beneficial for the deceased one.
The Prophet ﷺ said
“There is no deceased person on whom a group of people from the Muslims whose count reaches 100, are praying, interceding for him that except their intercession will be accepted.”
And in another narration:
“He will be forgiven.”
And Allah will forgive the deceased one even if the number is less than 100 as long as they are proper Muslims without any mixture of Shirk in their Tawheed:
As he, ﷺ said,
“There is no Muslim who dies, and 40 people stand up and pray funeral prayer on him, without associating anything with Allah, except that their intercession will be accepted.”