Good thing I chose now to come out of temporary hiding, eh?
First, I don't want to waste time addressing the fixtures that may or may not have profiles. While important, it's not critical. Remember that profiles are merely for use humans to relate to the program with, as well as allow the program to do all sorts of nifty goodness for us by becoming aware of features and functionality. A well made profile is a good thing!
So, onto the MIDI triggering: You got it right: two laptops/computers and 2 MIDI interfaces of your choosing.
Although I am an audio engineer, I am working on a show that involves a movie being played back, and unfortunately I need to be away from the playback units to trigger lighting, but the lighting is heavily synced, synced so well if I hit my first cue I'm done for the show.
So, I hear what you want to do, and what you want to do is entirely possible, provided you have a second laptop and MIDI interface for that laptop. And really, honestly speaking, this is the best way to go about it. Seriously.
No doubt you've made your scenes. Then the key is to program in your MIDI triggers, which I will leave that to you. Your MIDI triggers will be NOTE ON commands only for scene triggering. You may need a 88-note keyboard or else a way to trigger the notes from within Sonar. I use Sonar but honestly I'm not super familiar with it. I'm also at Sonar Home 6, which for my purposes is fine.
You need to be aware that MyDMX is a bit "thick" when it comes to MIDI. For your part, I suggest dedicating a port on the 8X8 for MyDMX and put a piece of tape on the interface to notate that. Now, get yourself an inexpensive M-Audio MIDI interface(a 2X2 or smaller because it doesn't make sense to have more than that for the MyDMX machine). MyDMX will gladly eat any MIDI channel and MIDI NOTE you can spit at it. Also, document and save often should MyDMX lose stuff(and it will if it crashes)
Go MIDI OUT on 8X8 port 8 on the Sonar machine to the MIDI IN on the MyDMX machine. Right mouse click to learn triggers in the USER tab, send trigger, it learns, the window vanishes. Repeat. By documenting your note values, you can now program this into Sonar.
Do recall that MyDMX scenes are time-based. I mean as in a physical time, not any sort of internal clocking. So, you can't make a scene run longer or slower or shorter. If the scene is 25 seconds and it has a 3 second fade-in, that's how the scene is going to run, period. Once you accept this, you're gold. MyDMX does NOT work via MTC, SMPTE, MMC, MIDI clock or any other syncronization.
I also suggest setting your scenes to be a lot longer than you need them to be so that way you don't have to worry about holding, or else set them to endless repeat for the same reason. It would suck to have a scene crap out on you in the middle of your song because you timed it too short. The worse case is it should go to the last step and hold.
Now, back to the MyDMX machine: Always keep MyDMX as the foreground application, which is necessary for MyDMX to work with MIDI triggering. Since you're dedicating hardware to this, this will not be one of your problems. But, if things stop working, this also gives you a quick place to start looking as it can be super easy to accidentally click a wrong location and MyDMX is not in the foreground.
Again, back to Sonar: Document your choice for triggers(They are notes) and simply dedicate a track or tracks in Sonar for these notes to be entered. Dedicate a port for MyDMX triggering as a quiet interface is a happy interface.
Also, keep in mind, there are 128 MIDI notes per MIDI channel, but MyDMX seems to have a hard limitation of like 249 scenes, so you'd need at most only 2 MIDI channels.
If you do it right, then you will meet your objective. Honestly, I'm against musicians doing their own sound and lights because it distracts from the performance that the performers are trying to do. At least with your method, you're trying to minimize that. Once the song rolls, it's performing time, not "tweak gear time".
A last bit of advise: END every song with your "break" scene. That way when the song is done, you trigger the scene for you guys in between scenes. EVEN if you end the song in a blackout, let the blackout hold for the time you want, then fade up that between songs scene. It will look cool.
Other tips:
Make 3 blackouts:
instant
Slow fade(+5 seconds)
Fast Fade: 3 seconds or less.
For your in between:
Depends what you want, but a 2-3 second fade up works nice. I like to use white at 100%, but that's just me.
Additional stuff:
If you want to get really advanced, you can directly control channels in MyDMX using CC information. Assign a CC controller to a channel, and you can quite literally have real-time control over your gear if you sequence the information. What's cool about this is that you can speed/slow your tempo and the programming will folloow this. This is advanced and can clog your MIDI data stream if over-used. With 512 possible CC controllers, that's 4 MIDI channels!(All of those can also be used for triggers as well). Really cool for movers and other intels, and even with color changers.