I've been on press checks at numerous vendors in the USA as well as in Asia. I prefer to go into the press-room and talk directly to the operator (or when in the Asia, converse through your customer service rep). During one press check in Asia I requested that the sheets be dried (with blow driers) before I could comment. The dry back played a significant role on how the color behaved on uncoated stock. For jackets/covers, we asked that the sheets be laminated before commenting. I'm sure this is the cause for frustration at the printer, but it's how we always do it. My biggest takeaway, though, is to not tell the press operator what moves to make, simply tell him how you feel about the color, let him decide what to do from there. That way, you are working together as a team.