If you have a smoker, you'll never get rid of the smells. If you have cat urine, you need a cat urine bacteria eater on the source.
Pretty much for everything else: Wash all cloth items. Wash with a touch of bleach all hard surface areas (including the ceiling). If you have carpeting, shampoo the carpets. Then open all the windows and let it air out.
Or.... build a really smokey fire right beside the camper and let all the smoke just penetrate everything. It won't smell like "people" any more! It will smell like Vienna Sausage!