I don't have this problem and this is what I do.

Wash twice a week at sixty degrees with Napisan and a normal washing tablet.
Dry either outside or inside as weather permits.

A strip wash is to strip excess washing powder in the nappies and is just a basic wash without adding and detergent.

Also, your son may have stinky wees due to an infection or slight dehydration - or they're really wet so need changing more often. May not be the case but worth bearing in mind.