Jim, there is a bit of a legal thing here I think.... as an independent carpet cleaner you are not licensed to be a "pest controller" as such. So I think you have to sell a service more under the heading of "containment".
Mostly, it's completely opposite to carpet cleaning. Forget the traffic lanes and open areas; you have to drag all the wardrobes, sideboards, chests of drawers etc away from the walls and get to all the bits of carpet that don't normally see the light of day.
First job, go round and shake all the curtains and swat any adults that are still hanging around, because they tend to hide in curtain folds.
Vacuum vacuum vacuum, using a handi-groomer to really agitate the carpet and cylinder vac with upholstery tool. All hands and knees work.
Then your options are either apply insecticide or HWE. I don't subscribe to the theory that colloidal products will kill these things. You can physically remove the adults, larvae and pupae from the house but you can't ever get 100% of the eggs out from the bottom of the carpet and you can't kill them even with insecticides. So eggs can keep on hatching and you'll get more moths coming back.
I apply a growth hormone regulator which works up to 3 months after application. Won't stop the eggs hatching but when the larvae start munching on the treated carpet, the chemical will stop them from pupating and thus breaks the life cycle.
I think you would need to get some sort of licence for use of such chemicals though. It's part of my franchise licence, which is handy.