Use a large bowl or washtub, making sure you have sufficient space to ensure you can wash all the pockets and sections of the product easily. Use warm water (not hot, because it could cause the colors to fade). Then using a soft brush (for example a shoe brush), apply some neutral soap and start to brush. Use an old toothbrush to treat obstinate stains.
Repeat the operation several times and in all directions, changing the water if it becomes too dirty. Repeat procedure until the product is clean. Do not wash with other items because the colors may run.