I've gotten so much helpful information here I thought I'd post about our success with keeping my husband rash-free this time around, after he suffered through a pretty nasty one during his unsuccessful treatment in 2006. He's now in his 7th week of the 3rx treatment including Incivek, and has only occasional, light itching.
He started using a heavy moisturizer at the start of this treatment. I ordered a gallon of Biotone Pure Touch organic message cream from biotone.com: (http://www.biotone.com/PTOMC1G/organic-hypoallergenic-unscented-paraben-free-massage-cream) It does come in smaller quantities, but we are anticipating a long treatment and the gallon size is economical. It's the approximate consistency of lard, and contains organic shea butter, jojoba, sesame, sunflower and safflower oils. It's applied immediately after drying off from the shower. Since my husband suffers from heavy chills, we transfer about 1/3 cup of the cream from the gallon container to a glass cup and warm it in a small crock pot prior to him stepping in the shower. Heating the cream also makes it easier to spread on the skin.
My husband uses no soap anywhere on the body but the armpits. He takes short showers only every second or third day. Not an ideal hygienic model, but he is clean and literally comfortable in his skin, and shows no rash whatsoever.
Good luck and best wishes.