I agree with PP, your way is best. I use a small amount of washing powder (just enough to break up the water). I was using liquid detergent for a while but had problems with build up. I always do a cold rinse before washing.

I didn't realise soaking is bad for MCN's. I dry pail, but if DH changes a pooey nappy, he'll pop it in a bucket of water. Must tell him to stop that, otherwise he will be paying for replacements.