Hi Linda and welcome to the board.
I have a 3 year old entire boy, who always manages to wet his feathers when he wees, so I know about this smell!!
Entire boy Cavaliers do seem to produce smelly wee - I find the apple cider vinegar really helps though. Mine wouldn't drink the water with it in, and now I acutally mix it with equal volue of honey, and syringe about 1/2 tsp into their cheek pouch. TO start with you need to do it every day for about a month, then twice a week seems to be enough to maintain it.
This gets rid of the smell, and i just wash him underneath and the feathering once a day with a wet flannel.
The vinegar/honey mixture is also very good for yeast overgrowth situations, where the hair around the mouth and sometimes on the paws too, becomes very pink where it is in contact with saliva.