"Dude... I can't fuck you without prepping you first..." But damn, if it wasn't so tempting to just dive right on in there... If only they were girls or magical self lubing beings like in some of the stories... not that Sam's been reading... Well, maybe one or two...
It was weird pinning Dean against the shower wall. Not unpleasant. Just strange. The weight and bulk and size of Dean was so different from pinning Ruby a girl up a wall or a door or any solid space. Hell, he'd been known to hold a girl up during sex without a wall for support - somehow he doubted he'd have the balance or upper body strength to do that with Dean. Maybe they could try when they were close enough to a bed that if he dropped him he wouldn't smash his skull open.
Sam fumbled for something, anything, they could use as makeshift lube. "Just be patient for a bit longer. And stop," he nipped Dean's shoulder, "being," he nipped Dean's collarbone, "bossy," and then he nipped Dean's neck while he slicked up his fingers to prepare him.