As a top dress? Give it a week at least. LOL It's ground up ROCK sitting on the top of the soil it needs to be in contact with. It doesn't dissolve like Epsom salts and get right to the roots, but will work its way down with regular watering.
If by 'coarse stuff', you mean the granulated/pelletized, that is actually powdered lime in a dissolving binder that makes it easier to work with. Check it for yourself. Put about a tbl in a glass of water. In a bit, you will have brown water from the dissolved binder and powdered/ground lime on the bottom of the glass.
If this is what happens, there is no need to grind it up. Just sprinkle it on the surface and water as normal.
*I* use 2tbl/gallon of mix, or 1cup/cf of mix.
Wet