The extra attention to his cock earns Crowley a whimper, and Castiel's so gone that he can't even be slightly embarrassed that he's been reduced to whimpering for a demon. He slowly comes out of his fog as Crowley pays some astonishingly delightful attention to his skin, and he finds he doesn't mind Crowley marking him, once he realizes what Crowley's doing. It will fade soon enough, but Castiel will delay that for him, if he likes it so much. He's sure that in what they just did, Crowley indulged him considerably, so he can indulge him in this.

Crowley's obvious enjoyment of the situation -- obvious for more reasons than the cock he's currently grinding into him -- is something to wonder at. Not with too much awe or reverence, obviously, just curious, as he's never experienced anyone else's desire for him like this.

"That was incredible." He feels a compliment is in order. That's polite, right? Then he reaches between them and curls his hand around Crowley's cock.

"What would you like me to do for you?"