Fabrizio, you asked if tanks, reels etc need to be dry, the answer is yes but only the reels unless they are the stainless steel type. Most plastic reels won;t load id wet or even slightly damp.

Pre-wetting is supposed to stop air bells but when I did some tests 3 years ago I found air bells can form at any stage in a process cycle regardless of a pre wet or not, they occur in dev, stop, fix and washing.