How to share Mac audio over Skype with the microphone? System:  2011 iMac, built-in microphone, Mountain Lion.

This is a two part question.  First the more basic scenario, second the more-niche scenario that I hope to ultimately solve.

I want to share my Mac audio over Skype, while still being able to simultaneously talk to the person on the other end of the call.  As of yet, every combination of options I have tried (dozens) involving Soundflower, aggregated devices, and even LineIn.app has completely failed.  

So firstly, what are the precise steps needed to get my Mac audio (say, youtube videos playing in a browser...) to transmit over Skype along WITH my voice from the built-in Mic?

Now for the ultimate solution I hope to achieve.  I want to be able to collaborate musically with other parties, using a program called Reason from Propellerhead Software.  Reason has its own audio interface setting - a single setting for both input and output.  I use the Propellerhead's own audio interface called "Balance" as my audio device for the software, providing my physical I/O as well as a headphone mix.

I want to be able to merge the audio output of Reason, along with my voice via the built-in mic of the Mac, and send them together over Skype so that the other person can hear what I'm doing in reasonable fidelity (subject to Skype's limitations, of course).

Can anyone provide the exact steps to share Reason's audio along with my mic, over Skype?

If 3rd party software beyond SoundFlower/LineIn is required, I'm OK with that... though this should work with just SoundFlower even.  I even had it working a couple months ago but can't seem to replicate the result again.
Turns out I had some strange Core Audio driver issue.  Every time Skype was running, process "coreaudiod" would fire up and begin to hog CPU like crazy.  I fixed permissions on my boot volume and it fixed a bunch of stuff related to iTunes, which apparently also fixed whatever was going on.

Once the coreaudiod issue was resolved, here's the setup that is working perfectly:


Skype "microphone" (input) set to Soundflower (2ch)
Aggregate Device created, consisting of Built-In Microphone and Soundflower (2 ch.)
Reason set to use the Aggregate Device
SoundflowerBed set to output to Balance.


Now all I have to do is create an audio track and enable monitoring, and I can hear myself in the mic, while normal Reason audio flows out both to Skype and my Balance to my headphones, and all is well with the world.