I use Petsilk clean scent conditioner on Benji. It's less greasy if you dilute it and make sure you rinse really, really well. Benji still looks and smells great a week or more after his bath. I also brush him a couple of times a day which I'm sure helps to keep him clean.
I shampoo him with wonderful handmade goats' milk soap that's made near me. (Their people soap is great too!) I met the lady who makes it at a dog park fundraiser. Her son had sensitive skin so she started making soap for him. The company grew from there.
Magic Moon Goat Milk Soaps