Obviously everything depends on your team's individual makeup and fatigue levels, but in general in a scenario like you are describing I would most likely do this:
Rank your starters 1-4 on effectiveness. Season ERA is an ok starting point, but it's not a bad idea to dig a little deeper and get opponent specific; if your opponent was 2nd in the league in HRs and one of your starters gives up significantly more HRs than the other 3, you might want to downgrade that guy. If your opponent led the league in walks and one of your starters walked a bunch of guys, you might want to downgrade him. Et cetera.
Move your #3 starter (effectiveness, not regular season starter #3) to Long A. Put the remaining 3 guys in the rotation. Make sure that dude #4 is Starter #3 so he won't start twice in a 5-game series. Ordering of #1 and #2 is situational and not extremely important.
Move your Long A guy to Long B or mopup (or rest if you want, but mopup at least will protect your other arms in the event of a blowout).
There's not a lot you can do to make sure your best relievers are chosen in close games. Put the better ones at Setup A and the lesser ones at Setup B and hope for the best. The lead at which Sparky switches to Bs is bigger than I would generally prefer, especially in postseason play, but there's not a lot you can do to game the system.
With all of this being said, in the case of your particular team I'd probably be inclined to make Liriano the Long A and leave the 3 Johans in the rotation. You just don't have enough long arms to work around the guaranteed short outing Liriano would give you. You could, however, consider throwing Liriano out there in Game 5, if it comes to that and if you'll have a Johan in the 90s or 100 who can follow him into the game if he only goes 2.2.