If you have made your various 'parts' as groups or component-instances [i.e. the 'right way' to set up a model] you can then set View > Component Edit toggles, to hide the rest of the model and/or similar components while you edit - in this way clutter can be reduced. Also using Layers for these various parts allows you to 'switch off' objects that are not needed immediately and so open up what can be seen. Having some Scene tabs set that remember a View and its Layer settings lets you quickly go back to the previous state. Also if you want to get inside single objects, then a Section-Plane placed on a main face can give you uncluttered access to the object's insides...