Really? You want him end up on the pavement? You need to know how to use both brakes.
IMHO on a full-out supersport (zx6r/R6/etc) you really shouldn't even touch the rear brake in a true emergency stop.
For me, the limit of traction is when my front wheel is *slightly* starting to weave or lose traction while the rear tire is *barely* on the ground (really only to keep the bike in a straight line). If you try to touch the rear in this situation you will lock it up. Granted, from a pure physics perspective you can stop faster if you can use both brakes as much as traction will allow but personally I'm better at front only especially since I have multiple bikes. Also using front only makes it a lot easier to subconsciously load the front suspension before clamping down.
I like to bring 2 cones (and a helper) to a parking lot to practice emergency braking. Have your helper use the cones to indicate when you start to brake and when you stop. If you haven't done this before you'd be amazed at how much improvement there is to be had. Think about it - how often do you FULL panic stop on a motorcycle? Maybe once a year? However in the rare occurrence when you need to stop like this the difference between 5 feet can be life or death so it's good to be in practice.
That being said, I sometimes feather the rear a bit during low speed to help with balance. I also use it at red lights so I can sit up (only after I have two stopped cars behind me). I used to play around with trail braking but it's usually not required if the bike is setup properly.
2 finger braking comment - totally legitimate. I two (or three) finger brake a supersport. Any cruiser should be 4 finger braking. Your lever needs to be adjusted where you CANNOT smash your fingers (the guy that is on the shortest setting probably can, and as someone else said - that won't affect the feel)
Master cylinder vs lines - Here's the thing, most people replace their lines when they bleed their brakes for the first time. Yeah you go from mushy rubber to SS wrapped but *most* of the improved feel has to do with getting rid of the polluted old brake fluid. That being said, I do feel like SS lines make a difference on the track when your fluid is getting extremely hot and all that.
Basically I disagree that replacing your master cylinder is going to make much of a difference on the street unless you need to change piston sizes or have an older non-radial setup.