Whatever ya do, do NOT run with the blades off!!!
You will most certainly over-rev the engine and the heli's parts.
Personally, I'v never had a new Engine in a heli, bought all mine used ( Whole heli with a demo flight first ).
As for using a test stand, I see no reason why not;
I'd say use the same prop you would use on that size engine for breaking in a non heli engine if on a test stand.
That is, slightly smaller than normal for the engine.

But I am not the expert here!
Read the manufacturers instructions, they should say how to break it in!

now wheres my Ray's manual, I'm sure He said something about it...

Russell