She stored chakra in her forhead for years, she has the chakra control, he seal release burst of chakra out, she system is strong enough to manage powerful chakra, just because the seal pumps burst of chakra like it does. Also, he chakra control alone should be enough. MY theory is that Katsuyu can reverse the channeling process,and allow Sakura to channel her Sakura as opposed to Katsuyu channeling Sakura's.
If Minato can ass pull it, Sakura defiantly can.
He had to learn it when he was alive, the Edo just gave him a stronger body, Sakura is basically a living Edo.