Brute force or not, they don't have what it takes to unseal something in a flash. Minato was hyped to be a sealing expert. Kyuubi was sealed. Unsealing it so it can be transfered. Same principle.
Well if you read the Manga then you'll know that Kurama is connected to his chakra and can feel it, he did this with Kin and Gin's and Yin Kurama felt like something was wrong so asked Minato to use his sensory ability. If you read the manga when Hashirama was telling Sasuke his story then you'll know that Tobirama said he didn't sense anything because he wasn't kneading chakra
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. Also Karin stopped herself from looking for Danzo when Cei was trying to find her
You being a smart but is not appreciated. I've been saying this for quite a while, but now it's undeniable. Do you exist only to criticize others or something?