I am assuming that because of the age, that it is a steel or aluminum siding. If it is bubbling or peeling, it probably had an adhesion problem in those areas. With metal sidings, the best thing to do is remove all loose paint, by scraping or powerwashing or both preferably. Make sure to remove all of the chalky substance from the metal surface before priming. If the chalky substance is not removed, it could cause an adhesion problem in the future. Then spot prime bare areas with an acrylic latex exterior primer. Then top coat with a good acrylic latex exterior paint.
It's may be a good idea to contact your local paint store and have a paint rep come out and take a look and advise on what you should do based on what they see.