Hmm you mean luck? He simply transplanted Hashirama's dna into them.. and saw who survived.. and Yamato succeeded.
They could always do what Orochimaru did and dig up Hashi-
Oooooh, right. The whole ethics thing.
Then there's the thing about him being a successful DNA spliced experiment that lived.
Now where did she have Orochimaru's notes to create Hashirama's dna arm, that matched Narutos body. Not transplanting the dna inside of him.