If you have two cardboard boxes, reasonably sturdy, you can use them to hold up the rear bumper. It is then much easier to do it with one person. Cut the boxes to ensure you are holding the bumper at approximately the correct height.

I did it in 4.5 hours, myself, and only had to pause to find the correct Torx bits. I didn't drop the exhaust completely, I just dropped it enough to get the socket extension up to the bolts. I sat the exhaust on jack stands to make sure it didn't sag too far down.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue