That tickles. And doesn't discourage Dean from what he's doing. Actually, it has the opposite effect because if there's one thing he knows, it's the sound of someone really, truly enjoying something and that heavy breathing is one of the hallmarks of 'this is amazing.'

It's pretty difficult to settle against the headboard and get Cas back into his lap without taking his hand of Cas's back, but he manages somehow. Once they're both...as comfortable as they can be, given the buttoned up state of their jeans, Dean goes back to what he was doing, tracing the outlines of Cas' shoulder blades, pressing the tips of his fingers against the ridges of Cas' spine, following the lines of muscle on his back. It doesn't make a lot of sense to Dean, but it seems to be working for Cas and hey, there are few things Dean likes more than lying back and watching other people really enjoying themselves.