Do be aware that the chances of a successful boar trio aren’t great. Usually it ends in fights and broken bonds.
If you do intend to go ahead with attempting a boar trio then ensure the cage covers at least 300x100cm (approx a 9x3 c&c cage) (a boar trio require a huge amount more space than normal cage sizing requirement) that there is at least three of every item and that all hides have two exits. Having a cage of that size won’t make them be able to get on (boars find it very hard to form a functioning hierarchy when there is more than two) but lack of space will cause fights.
The most likely outcome is that honey and coco won’t accept your piggy, but there is also the risk that trying to introduce your piggy can cause honey and coco to also fall out and need to be kept separate from each other going forward.
It would be a good idea for your friend to have these piggies checked by a vet.
If they have not been well cared for, there could be all kinds of other issues and putting products in them/bathing them could mask signs a vet may need to diagnose and treat any issues.
Adding More Guinea Pigs Or Merging Pairs – What Works And What Not?
Bathing (including cleaning grease glands)