I take 3 lugs from the crusher, drop a level teaspoon on top of it, then work it in to the must using a punch down tool.
The reason for doing this is to stun any existing wild yeast (and/or bacteria). Once 24 hours passes, the level of free SO2 will drop considerably, making it safe to introduce yeast.
If you find that you need to add water, I would add it AFTER the 24 hour waiting period and add no additional k-meta until after fermentation / MLF is complete.