Decided to record some basic actions on ZB and inspect the generated scripts and found answers to most of my questions.
There are still some bits that I can't get from recorded sessions and still require help, though.
1- How can I get/set the current brush through ZScript?
Found how to set the current brush (using IPress)
Still have to find out how to GET the current brush
2- Can I set brush settings (like zIntensity, radius, etc) directly through ZScript?
Covered: [ISet,Draw
raw Size,X], [ISet,Draw:Focal Shift, X], etc
3- Can I call functions from an app/dll implemented in C# from ZScript?
Got it too: FileExecute.
4- Can a ZScript run in an infinite loop for as long as it is active without freezing the app?
I guess Sleep/Sleepagain would be just the thing... if only they would take fractions of a second... will have to think a little more about this one.
5- Can an external app cause ZB to run a specific script without sending keyboard messages?

The biggest chalange so far. Really need help whith this one! Please!
By the way, found the links to the ZScript Ref:
http://www.pixologic.com/docs/index.php/ZScript_Basics
http://www.pixologic.com/docs/index.php/ZScript_Command_Reference