Stairs teaches the quick swing with a slight uppercut to get elevation.
But he also teaches working the count.
Power and discipline go together, Joe Morgan and MIke Schmidt are the two best examples.
Aggression simply means you attack your pitch. With today's fireballers, you need a quick bat and solid contact, physics will do the rest.
Now Stairs teaches they should take pitches the first time at bat, there are a number of good reasons for this:
1) see the pitcher's repertoire, and for the first few batters, let your teammates see it as well
2) time the pitcher
3) run up the pitcher's pitch count so he doesn't get to the 7th or 8th inning
Nothing worse that letting the opposing pitcher get through the first inning with 7-8 pitches
Once you know what he has, and how he's throwing, you can adjust, if he's throwing strikes, attack early, if not, let him fall behind in the count.
Galvis has always been overaggressive, but last year he improved his mechanics and shortened his swing.
Franco when he's patient has a short swing with plenty of power, when he's aggressive he swings from the heels and it lengthens.
Proper swing mechanics generate power, look at Hernandez this year, as he gets stronger, he generates more power naturally.
Guys like Franco, Joseph, Rupp and Altherr have enough power to hit it out of anywhere in a ballpark (see Joseph's CF blast), so the key is just making solid contact, not swinging from the heels. The CF alleys are your friend.
For guys like Hernandez, Herrera and Galvis, the key is go with the pitch, but if they try to throw it inside, pull it deep, but take the outside pitch the other way, because you're not strong enough to power it. Herrera had a perfect inside out hit to LF last night.
I think some power hitters fall in love with long HRs, but Hank Aaron understood that a 400 ft HR counted the same as a 450 ft HR.