Here's a touch I can't remember if Ken put into the instructions or not...
Lay the envelope on a table and coil the thread loosely onto it (dropping from above)... then fold the envelope in half, trapping the thread inside the fold.
I hope this explanation is clear.
Now you can put the envelope into your jacket pocket.
When you need the envelope, take it out, let it unfold with the thread TOWARD the audience, and then snap the envelope at the rear (side toward you) sharply, with your index finger, snapping off your thumb.
This causes the thread to shoot strait out toward the audience and invisibly, drop down, untangled.
Proceed with routine. :genii: