Your chosen lens will breed a knowledge of the proximity you need to gain to your subject, without the necessity of the viewfinder.
Shooting from the hip, out on the street will produce within you an intention and a knowledge of your kit that must be practised and implemented, so that you can feel your focus lock and your shutter fire, under your fingertips. Your chosen lens will breed a knowledge of the proximity you need to gain to your subject, without the necessity of the viewfinder. Intentions are rarely the same as the reality, but they allow you to take an educated stance from which to work.