If anything, Sam might say that Castiel enjoys it more than he does. Which is perfectly fine, of course. Sam definitely enjoys watching him enjoy himself.

"If you need to stop, Cas, hit the buttons on the phone." Chances of having to were pretty small, really, but there was a possibility. "For now, if you're okay, I want you to grab the lube and coat your fingers. You're going to open yourself up for me."