Abhilash, as this is a foreign breed, it takes time for this dog to adjust themselves in the local climate. Remember, Labrador developed in England which is a very cold country. In hot climate, Labrador will loose all it's thick fur so that soft fur can trap air and keep the body cool. Likewise, in Winters, they loose soft fur and gain thick coat which helps them generate heat in their body. It's all natural process.
The shedding should now stop. You are using a right brush. However, try not to brush him inside the flat. Take him out of the house, like in a park and then brush him all over as this will ensure that the dead fur are disposed off outside the house and they won't cause menace in your neighborhood.
You can use Nutricoat or any other hair supplement available for dogs in the market.