Hi
We clean a block of flats with 16 Juilett Balcony's as per the photo (taken when flats were still under construction. I use a 10" Vikan oval brush directly coupled to an Ali Unger Teleplus Pole using a brush to Unger adaptor.
If you feed the brush in between the bars at an angle and slightly to one side, it will go it fine - just takes a little practise. I clean the top of the windows/doors above the bars first. I then start on the window/door section behind the bars. I only need to insert the brush into the middle bar of the window section to clean; then by brushing up and down and moving side ways to the left and right as I go, I can finish the hole panel section with one brush insertion - then remove brush at an angle and move onto the next section.
Finally, I insert the brush up under the bars as clean the low section of window.
You won't be able the clean the window/door sill.
I know one one local cleaning company that wont do the balcony's as they say the customers can clean them themselves safely from the inside.
Spruce