What if it was a sapphic slave auction? Use the same showing off/revealing strategy?Well fortunately I have a lot of experience with public speaking so some of the methods would be the same. For example eye contact, you want him to know this is for him, so you look him directly in the eye.
A smile, wink, blow someone a kiss. All good initiators without commitment, see if he responds. Does he run his eyes over your body or is he busy talking to to his buddy next to him? Is his facial expression engaged or does he look bored? If you get positive indicators then you move onto more serious stuff. If not don't waste anymore time on him.
If you find he has an interest then you direct more serious things towards him. A slow sensual pursing of the lips like he was something delicious you wanted to eat. Make sure when walking around the stage to put one foot in front of the other (watch super models) as it makes your hips swing and your breasts bounce more. When turning around keep face forward as long as you can before swinging your face to the approaching side, nobody cares about the back of your head.
Throw your hair over your head and then flip it back.
Run your palms over your curves as far down your body as you can without bending over and when bringing your hands back up your body make sure they pass over your sex (DON'T play with yourself, he is buying you to entertain him not yourself) and up your belly before you cup your breasts. Run your finger tips over your areolas and nipples.
And some point make sure you do bend over but don't let your shoulders get level with your hips. I have never met a guy who didn't like the sight of dangling breasts.
Now if I was bigger chested (I'm a "B") I might lightly lick my nipples when displaying them because I could keep eye contact with the buyer while doing that. Believe me he is not thinking what my tongue might do for my nipples (no matter how much he likes that), he is thinking what my tongue might do for his anatomy.
The types of things you see in modern BDSM (checking out sex and ass) probably didn't happen in an auction setting. When you buy a horse (or any live stock) you do the physical exam in the stall before the animal comes out for bidding. Once the bidding starts the auctioneer has no time for you to poke at the subject, he wants to get as many thru the sale as possible before the buyers lose interest (and they do).
Don't concentrate on just one man, find several in the audience who you think are good candidates. These are highly successful powerful men with egos. A lot of the conversation around the lectus was 'I did this or I own that'. Very much like modern rich guys. They love nothing better than one upping their social peers. If you can get several of them interested a bidding war starts which is only in your favor because he is less likely to discard you (he doesn't want to admit in front of his buddies buying you was a mistake) quickly. Plus a bidding war makes the seller very happy.