I use a flocked dual trim superlight with fan jets.
Ive modified it by turning the fans vertical and cut out the brush so the fans can spray through.
Because the superlight is so thin, you can get to the fascia board behind the guttering and i find having the fans vertical makes it easier for rinsing / applying tfr. Also the fact its so light makes the job much easier.
I've tried most brushes for fascias and found the modified superlight makes it quicker and less strain on the arms at height