Hi Paolo. I don't really post here anymore (not since 2011 I believe?) but I do creep the forums sometimes and more regularly now that I'm posting my progress on my own blog with going Caveman. I was previously water-only since 2011 and I experienced congestion on my forehead and chin and dehydration. My acne cleared up but since maybe the summer my skin started getting oilier-looking and more congested on my forehead so for the last ~3 weeks I've been on no-wash. I'm not strict about it, my mantra is basically "don't wash your face on purpose" so I basically just ignore my face. Whatever water gets on it while showering (not usually a lot, more so in the form of minor splashing or sprays of water) is what constitutes a washing for me, then I pat my face down. I rubbed my face down a couple of times and it definitely did make my face oilier-looking, and made my marks look much worse for a day (in my opinion). I assume I might keep doing that as I see fit, and hopefully it will need to be done less and less. I do find that exfoliating like that results in me being more likely to break out as it definitely irritates my face.
But basically, my advice to you would be to stop over-analyzing it and to not over-think your actions. Follow your intuition, but if you are determined to stick to a product-free routine then keep those instincts within this type of routine. So I'd not say moisturize unless you feel that it really is required. But my face felt really uncomfortable when I first went water-only and it eventually settled down.
I've done Caveman off and off in 2010-11 and was water-only (rinsing once a day or less) since 2011, so I definitely have some experience with this. I have 2 zits rihgt now from picking and from using lotion on my body, but otherwise things are getting better for the most part. It's just the clogging that I have to wait out. I check back regularly enough so if you need further advice or whatever feel free to post