I've helped hire 3 software engineers to both work with me and mentor me and they were all failures.

First two hires quit after only a few weeks.

Third hire was temporarily successful. He eventually revealed himself to be both a jerk and not very technically skilled, so I spoke to higher-ups to get him removed.

My hiring strategy was designed to be simple and respectful. A simple, 20 minute assignment completed between phone screening and on-site. And 2 on-site interviews. Despite the 3 failures, I still feel like it's a good strategy. But evidence says otherwise!