If one could be lucky and find one in one go, then it was okay, but the reality couldn't work that way since most of them failed, so instead of confessing, one should try to be the closest existence to the girl then used another girl to test the feeling of the girl.
While most will think that it was him who came up with this jutsu but he was just using his knowledge of the plot so it will always be minato who came up with this jutsu; he wasn't shameless enough to take credit for that.
"You bullied Lady Leviathan's Magical Girl Series through an anonymous account online, almost sending her into depression… Can you believe that one of the Four Great Satans shivers at the mention of someone called NoobGamer69?"
"You attached wheat and oats on Rias' head and watched her getting chased by a dozen hungry camels for half an hour, knowing very well that she's scared of them."