Me use my Sampoo to wash and soak it in warm water, wash the
same as you would as your SAF combat helmet 
But my advice don't use force to scrub, the padding will come off,
simple scrubing would do, rinse, drain water out and leave it under
hot sun to dry!
If hot sun not avaliable, use a bucket or pail, turn your helmet
over and let the water drain into the bucket or pai. Last thing you
need is a wet floor!