Dylan Bell, Matthew Castles and Benjamin Flegg have been charged over the incident which occurred at a western Victorian prison last year.

Bell and Castles faced the Ballarat Magistrates' Court on Friday by a video link from a prison, while Flegg was absent for the special mention hearing.

Police prosecutor Sergeant Simon Pearce said the victim was in his cell working on a painting when the three co-accused entered and forced him onto his bed.

He said they used a trouser belt to bound the man's hands and legs together and placed a sock in his mouth to gag him.

Police allege the prisoners then pushed a paint brush into the victim's anus and removed it when someone was heard walking in the hallway.

CCTV footage allegedly shows the three accused men entering the victim's cell, with one man carrying a trouser belt.

Sergeant Pearce said later, the prisoners were in another area when they held the victim down on a couch and broke wind on him.

The men, who have been charged with sexual assault, will return to the online court for a contested hearing at a date to be fixed.

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