Every roof cleaning job is different, and there is more then one way to skin a Cat.
Some like Gutter Canes (we don't)
We feel Containment (bagging) of run off is always best.
Yes, you can use a Gutter Cane, and plug up the downspouts with sponges or little Footballs. LOL, we once saw a stupid roof cleaning company from Orlando come here to Tampa, and do this right next to us, on a job we were doing.
Well, the gutters filled with water, then guess what ?
The freaking Gutter broke away from the house, bent, and crashed to the ground!
Lesson Learned, for that crew, I hope ?
Gutters are designed to FLOW water away from the house, into the downspouts.
They are not Water Storage Devices.
Gutter Repair Guys lick their chops after a good hard rain. They know that clogged gutters can't last very long, in a good rain.
Another problem with using Gutter Canes is they reduce water flow and pressure!
We use dedicated ground men, and want them to have all the water pressure that a home has to give.
Hard to do when a gutter cane is up there sucking up all the water pressure and flow.
Here is a discussion on this subject http://roof-cleaning-institute.activeboard.com/t49881681/using-gutter-canes/
I pulled up in a quick search of the Roof Cleaning Instutute. It has pro and con for gutter canes vs bagging vs gutter extenders.
There are probably 25 of these types of threads at the RCIA Forum, I just don't have the time or energy right now, to do a complete search.