Sam and Cas would be all about kisses.
Slow, sweet kisses while cuddling together on some motel bed. Maybe they were watching tv with Dean at first but they weren’t into whatever was on and it just kind of went from there. And when Dean finally notices he makes a big fuss and goes, “Dudes, gross!” but he secretly loves that they’re happy together. And Dean’ll grumble about going out to the bar or else his life really is going to turn into a porno and Cas looks confused and Sam rolls his eyes and pulls Cas right back in for more kisses. Maybe they just kiss and kiss and hold each other until they fall asleep so entangled that they don’t even remember that they’re separate people and not just one soul connected in love.