Care should be taken when cleaning components in the engine or other places with movable parts, hose attachments and the like. But the same attention to detail should be given under the cowl and in the gear wells, if you have retractable landing gear. The task of cleaning cylinders, lines and hoses is tedious, but what you may find could potentially save your life. An overall visual inspection is great, but you are likely to find a lot more with a rag in your hand. And while the propeller is unlikely to be dirty enough to require a rub down, running your fingers along the leading edge will help you catch any dings or, worse, cracks.