Hi
I'm also now using a superlight brush to do the doors behind the juilet balcony's on some flats we do and don't need to use any swivel adaptors.
I find that the easiest way for me is to rotate the brush and stand to the side and the brush goes in quite easily. ( It's the same principle as manovering a chair through a doorway that won't go staright through.) The easiest brush to use was the old Vikan Ovals and, as they didn't need an angle adaptor, sat fairly square on the glass. Their drawback was that they were so heavy.
We start off by doing the top of the windows and doors above the balcony's as per normal. We have small openers on each side with a window vent so the brush needs to be at the correct angle to stop water ingress. As the bars we have to deal with are quite close to the glass, we have to set the angle adaptor in the straight position to get the brush in which does mean that the brush doesn't sit squarely on the glass but that isn't a problem really.
Spruce