Not how this works, sadly. We don't allow members to put out "feelers" or auctioning. Post your watch for sale which you're allowed to since you're a supporter and see if the market is interested. If the market is not interested, then you can withdraw it.
Most of these, if not all, are responses to Want To Buy posts on our sales section.
Other ways these originate are like seeing another member comment on a thread something in the lines of wanting a specific watch or not finding it. My favorite and the most important instance can be members who have become longtime friends and know what each other are looking for and they just want to do it through the forum.