Well, he can't see when he's distracted that way. It's hard enough to concentrate on buttons as it is, with Crowley's tongue fairly twisting around his own and Crowley's hands fingering interesting new shapes in his hair.

Twice he almost gives up and puts his arms around Crowley's neck or waist (depending on how far along he is, of course), but after what must have been hours, at last the buttons have all been pulled through their infernally tiny holes, the shirt hangs open and he can slide his hands underneath.