Sam waits, hands on Castiel and reminding him that somebody is there, somebody is close and helping. He turns to Dean, then nods to the bag. They're going to need some clothing for Castiel to change in to before they can get anywhere.

That, at least, is easy enough to handle. Shirt, jeans, underwear and socks. Shoes may or may not be too difficult, they'd have to see.

Once Dean hands them over, Sam turns back to Castiel. "Cas?" he asks as the former angel's eyes open again. "Good, Cas. I have some clothes here for you. Are you okay to get dressed on your own or do you want help?"

Keep giving him decisions to make. Even small things. Especially small things at the moment.