Chris, I've had many rv's with the alum. sides and I washed and hand waxed them just like a car. Be careful around any decals as some say not to get wax on them. If you have painted decals wax them. Its alot of work but will be worth it down the road. When you go camping its not hard to spot the rv's that are not taken care of.
Try to keep your rubber roof clean also as it will help in keeping the sides clean. Hope this helps.