The Boeing push is a technique that could be used to great effect on the 757 and the 767. It also works well with the A321 and 330, but it’s not a ‘day to day every time it works technique’. It’s only for when the aircraft doesn’t kiss the tarmac during a regular landing due to miss timing during the flare when flaring too early or too much. It wasn’t something one did on a DC10.
In essence, you flare but the main gear levels off slightly above the runway. As the aircraft slows and begins to settle, as it begins to sink towards terra firma, a slight forward push will help pick the gear up as the aircraft settles downwards, generally leading to a smooth touch down.
It goes without saying, that pushing forward too far, may have unintended consequences.
Its more of a bit of ‘fettling’ with the elevator during the flare rather than a definitive prescribed technique for each and every landing.
First time I saw it done, it frightened the life out of me. Eventually I was teaching it myself.