Sweeping bottom up: How to?

I need to sweep my open fireplace - the chimney is about 20'. but is 30' off the ground. The top 10' is unsupported - I'm not going up there on a ladder - I'm not 100% sure it wouldn't fall down, and that exposure with no way to clip into a roof line isn't working for me...

So, I need to sweep bottom up - what do people do to protect furniture/themselves from the inevitable soot storm that's going to ensue?

I have go big shop vac hose at the bottom of the flue and blow the exhaust outside in case the filter wasn't complete.
I roll up the carpet and tape down some plastic and put down newspaper, etc.

There might be a more scientific way to block off the bottom to insure that nothing gets past, but I've had pretty good luck, esp with the fine stuff.
Mine is a relatively new corregated stainless 6" liner though.

Like the shop vac idea - mine is clay flue (on the open fireplace) so I'm expecting a big mess - I have wondered about building a polythene tent....