|Liverpool Crown Court|
The pair, aged 12 and 14, are accused of attacking the woman in the Anfield area of Liverpool, England, in September 2014.
She was raped by the older boy, while the younger defendant threatened her with a knife and sexually assaulted her, the city's crown court heard.
Both boys, who cannot be named due to their age, deny all charges.
When paramedics found the woman, who has mental health difficulties, she was at the point of hypothermia, and was covered in paint, jurors heard.
'Unable to cope'
Prosecutors told the court the paint was poured over her head along with cleaning fluid to prevent the recovery of forensic evidence.
Ben Jones, prosecuting, said: "The prosecution case is that these two defendants, acting together subjected [the woman] to a humiliating sexual assault.
"The prosecution say the word 'humiliating' because the word is justified.
"Violent and sadistic might also be accurate descriptions."
Mr Jones said during police interviews the victim, who suffered 27 injuries, including bruising and scratches, described being "unable to cope" in the weeks afterwards.
The 14-year-old is accused of rape and three sexual assaults, while the 12-year-old is charged with two sexual assaults and aiding and abetting rape.
No charges for the use of the knife? Why not?
Both boys sat in court next to their parents.
The trial, which is expected to last for a week, continues.