There's just something about putting panties on a man. I'm not saying he turns immediately into a slut—not that it'd be a bad thing. No, a slut's a slut, and will always be a slut, panties or no. What I'm talking about is putting a pair of panties on a man, subsequently and instantly turning his man ass into a piece of ass that I want to pinch and smack and manhandle. Preferably it's a pair of transparent lace or mesh panties subtly covering a hint of asscrack, or perhaps a thong or tanga-cut pair of panties, that go right up his asscrack, leaving that bit of cheek peeking out below the fabric, that nice little piece of ass that I want to grab and squeeze and turn all kinds of deep shades of pink.
Before I put that freshly pantied piece of ass over my knee, why not apply a pair of stockings to the bitch-to-be, a pair of fishnet stockings or perhaps a lovely pair of sheer black stockings, attached to a garter belt of course. If that piece of ass didn't look like a slut then, he sure as fuck does now, he does enough for me to start calling him slut, put him over my knee and smack his slutty little ass.
There's nowhere else a slut should be than on his knees or getting bent over—bent over a table spreading that piece of ass, or bent over hands on the floor, showing off how limber that piece of ass is, or bent over my knee, ready to take a strict spanking to make that slutty piece of ass glow. A few quick taps all around both ass cheeks, and that piece of ass starts to flush. Is it blushing? Perhaps a little embarrassed to be bent over that way, hands and feet on the ground, ass sticking up in the air, begging for punishment? Oh yes it is, and that shy, demure, blushing little piece of ass inspires me, makes me want to smack it a little harder, a little faster, in smaller then wider circles, all around one ass cheek then the other ass cheek, turning that sweet little piece of ass hot pink, then bright screaming red. At that point, I'm spanking your little piece of ass so fast and so hard that the redness feels like it's hotter and faster than the rate you're squirming around on my lap, and you say, "Please, Mistress, please! Have mercy on your slut's hot little piece of ass!"
Obviously you wouldn't necessarily think to say that, which is why this is a fantasy. But that doesn't mean you can't practice. It's not a lot of words to have to remember, slut.