Quote - from the warehouse yes?
ok you've got coplanar faces - thats the streaking. add in the bad technique.

ok you need to remember here - most of the warehouse models are not modeled that well. this is not Sketchup but the modeler... that needs to be tidied up a lot.

So it is possible to model without these faces then? Great!

What is the best technique to apply in order to avoid these streaks?

Passion is anger and love combined. So if it looks angry, give it some love!