I believe I am familiar with the scenes you described. The woman, helplessly shackled into what amounted to a large, metallic sink (images I saw were titled "The Copper Sink"). Metal cuffs kept here wrists and ankles secures to the sides, maintaining her in a spread eagle lay. Metal pipe elevates her hips just a little off the surface of the sink (bottom in the air), forcing her to rest her chest more directly on the surface. Unless she arched her head backwards and propped it with her chin, she would have to lay her head down or one cheek or the other, causing her face to lay in whatever may have pooled in the closed sink.
When the activity was finished, she would get a thorough wash in the sink (I did not like the brush and would rather hand wash her). At one point she would flip over so her front side would be cleaned. The piping would still be in place, forcing her hips into the air, but this time, belly up. The hand sprayer was extensively utilized to rinse the area between her legs. I have wondered about the sensations she may experienced from the jets of water being sprayed between her legs.
Your response made me think of one thing I have never mentioned when visiting this site (although nobody may care). I draw the line on wincing pain and things terribly gross. I become too emotionally connected. I only want to bring pleasure and enjoyment.
I try to continually read and study details about the female anatomy and mind to understand the general likes and dislikes. It would break my heart to realize I have done something she did not like; therefore, this is why I spend so much effort to try to continually sense and monitor her breathing, heart rate, muscle movements, vocal expressions, swelling breasts, erect nipples, swollen and pulsing clitoris, even down to seeing if chill bumps form on her skin when she is touched.
Ultimately, I search for signals of a climatic vocal pattern, muscle contractions, body arching, or vibrating jitter in her body. Prior to that, I seek signals of excessive moisture, nipple and clit erections, or wrestling with the conflict of seeking the touch of my hands while trying to evaded them to regulate the flow of stimulation.
If she does not have a good time, then I do not have a good time. When finished, I hope she attacks me when she is released from her restraints, and does not let me go until I am thoroughly exhausted.