Personally I prefer to go the other way, not discuss the play at all in advance. I like the element of surprise. That said I am assuming you know all of her sexual likes - dislikes or at least most.

If it were me I would start the session by grabbing her hair or throat and pulling her to me so my face was in hers. I would tell her she needs to be taught how to suck cock and what happens if she doesn't give a good blowjob.

I'd slap her face and tell her she is going to do as she's told, then slam her body and face against the wall. Then put the collar cuffs on her. Come to think of it, the only thing I'd preplan is get her to wear old clothes. Then with her against the wall I'd whack her ass a few times (hard) to show her who is holding the crop and has the power. I'd shove my hand up her skirt and brutally grope her pussy, telling her what a slut she is because she's wet. And if she is going to be wet like a slut she's going to be treated like a slut.

I'd rip her clothes off or to shreds, (maybe need help of scissors). Leave her in tattered rags. I'd be often grabbing her hair and slapping her face. With face to wall I'd flog her, Make sure she has legs apart to flog that pussy. Then turn her around to flog her front. All the time I'd be warning her that if she doesnt suck cock good this is what she would be getting only much much harder and worse.

When she's warmed up, I'd force her to her knees, get my meat out (may be nice if she's blindfolded the whole time) and slap her face with my meat before making her lick and suck it while I give her precise instructions on what to do.

I may cum in her mouth or on her face, alternatively I may say she's done such a good job making me horny I'm going to fuck her. Then throw her on the bed, sofa or even back against the wall and give her a hard rough fuck with lots of verbal eg "that's it take it my sweet whore".

Ooooooooops did not mean to write so much. I got carried away. Anyhow you got the idea. Use some excuse to treat her rough, then just push her around and soften her up. I like the pretext of "this is whats going to happen if you dont do as told". Sometimes if giving heavy flogging caning or whatever, I like to give her the opportunity to end the beating by simply offering me something better to do eg sexual favors eg a blow job. And since I like body writing I would write suitable dgrading remarks all over her body.

This may not have helped you but it sure as shit helped me writing it down