User blog comment:Tekkphreke/Blut Vene and Blut Arterie/@comment-4207271-20131213042305/@comment-24282510-20131213042520

"Blut seems liek a technique that would take a long time to learn, kinda like Shunpo, how it has varying levels."

Agreed The way i took it tokes mere moments to switch between the two but Kubo's writing is not up to par so we may never know.