I don't see consent as an on-n-off switch. I see it as a spectrum of green yellow and red, with infinite shades in between. Since I work a lot with extreme physical conditions, impact and pain, I take it slowly. My movements are gradual and suggestive.
Each and every moment of a session, my model/play-partner feedbacks me with a shade. Most of the time they don't even do it consciously, their bodies do it for them, through the tightness of their muscles and their breathing. Sounds and facial expressions are a good indicator of things too; however, given the warzone environment of my Saturdays residency, I have also learned to work without. I try to keep every shade as close to green as possible. If a moment comes where the shade seems turning towards yellow, I backtrack on whatever I do. Due to that level of responsiveness, the trust between me and them grows even further; their sense of safety does too.
During the session I follow their lead. Together we explore what they desire to explore. If they eventually desire to go to their dark side and meet their demons, I'm happy to take them there too. I take them there, I stay with them, I hold their hand.