Tammy, what's your grooming routine with the girls? (They're beautiful, btw.)
The only way you can really stay on top of shedding is to keep up with the grooming - assuming of course that your cats are happy to be brushed. There are quite a few pretty useful grooming implements on the market that will cut down on the amount of fur being shed.
A good starting point would be a slicker brush, which is brilliant at removing loose undercoat. A fine-pitch metal comb is also handy, as is a good pure bristle brush. If the amount of fur being shed is quite copious, there's a product called a Furminator which should make inroads into the problem.
You don't need to spend vast amounts of time brushing your cats, just a few minutes each per day will really help. The act of grooming itself is a good coat conditioner as it distributes the natural oils throughout the fur.
Also, you might want to pop a few drops of evening primrose oil into your girl's food as it is a helpful supplement when dealing with skin and coat conditions.
In answer to another question on this thread, not sure whether particular brands of dried food can affect coat condition. Puffball, if the switch from Royal Canin to Hills was recommended by your vet, the chances are that your vet is a Hills stockist and therefore maintains a financial advantage by promoting and selling the product. If the shedding was a diet-related condition, IMHO either an exclusion diet (finding out what foods are the trigger) or a hypoallergenic diet (e.g. James Wellbeloved) should have been suggested.
