This shot is a highly skilled net shot which requires good co-ordination of the hand, racquet head, the racquet on the whole and perfect body balance to earn a point from this stroke because it has a controlled forearm rotation and grip tightening in the process. You hit the shuttle forward using a sideways action.
On a practical training session about learning the brush skill, it is important to improve the skills rather than losing a point. Place some shuttles (preferrably some damaged ones will do) on the upper net chord so that the feathers plunge into the upper portion of the net, so that they hold the shuttle in place with the cork pointing upwards. Now try the sideways brushing action for one shuttle at a time with a controlled forearm rotation and grip tightening. Take care the net movement will not dislodge any other shuttles you have attached. Try adding some movement towards the shuttle and also by jumping forward to play the kill.
Realisticaly speaking, when the shuttle is extremely tight to the net, you cannot play a normal net kill, because you’ll hit the net with your racket. In such circumstances change the stroke you play if you can’t play a brush stroke.
This stroke is practised on the forearm side than on the backhand side.