Urinary incontinence can be managed with belly bands. Faecal incontinence I would think would need dietary advice to keep the faeces as firm as possible and a regular feeding and toiletting routine.
I have found this website which has dog nappies including one for faecal incontinence........
All of this will be time consuming as these would need changing often. Problems would arise if the dog is not kept dry and clean.
Presumably the vet would have prescribed any medication that may help although I think most of the drugs are for female incontinence. I'm not a great believer in homeopathy but it may be worth the owner speaking to a homepathic vet to see if they know anything that could help.
Cavaliers......Tommy Tuppence 2000-2012 and a half share of Faith.
Japanese Chins.... Dandy, Benny, Bridgette and Hana.