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Castiel has never done any, in Dean Winchester's colorful phrase, 'cloud-seeding'. He has never engaged in sex, and does not understand the appeal well enough to attempt it. Sex requires bodies, and bodies are an inconvenience at best; sex is a sticky, sweaty, messy thing, and thus better avoided. Sex, judging by Sam and the pizza man, is a momentary physical connection, nothing more.
Castiel has stood with his multidimensional waveform self in the same space as that of his commander. Castiel has many times merged himself with Anael to strengthen the bond between them, to connect, communicate, and once, on orders, to create a new waveform, a new angel to fill a gap in another garrison. Castiel has experienced communion.
Dean never asks about that.