Brushing is best done using a 18" pool broom and a telescopic pole by starting at the waterline using short and swift vertical strokes as you move around the pool. Working from top to bottom follow this by brushing your steps, making sure to get into all nooks and crannies where algae likes to start growing. Next, sweep down the walls from the waterline to the floor while pulling the brush towards the wall, then do the same across the floor of the pool. There's no hiding that this is hard work and if done with some considerable effort you'll get a great upper body workout at the same time.
Stubborn algae may require the use of a 6" stainless steel algae brush for concrete/tiled/pebble/quartzon surfaces etc, and fibreglass with care. On vinyl liners only use a 6" nylon algae brush.
If waterline scum has formed then removing it by brushing only will be hard work, you may need a formulated product called BioGuard® Off The Wall pool surface cleaner. It has a pH of 7.5 which will not to affect your pool adversely.