I don't know whether this is any help. One of my customers told me about cleaning verticle blinds te one day. Apparantly you take the plastic chains off them and remove the weights at the bottom and the plastic insert at the top of the blind. Roll them up tight and secure with an elastic band. Put this with the rest of them inside a cotton pillow case and put on a low heat wash in your washing machine.
Take them out and hang them when still damp up to the window. Apparantly they will look curled for a little bit, but the weights in the bottom will straighten them back out. If you wait till there dry before hanging, you won't get the kinks out.
Even if you don't use this method for yourself, pass it on to your customer and earn some brownie points.
Dave