I tried to read quite a bit leading up to my harvest. My understanding is that is part of what it will do. You are not supposed to stir the buds around in the water so it's up to the water naturally causing the dirt to fall off the buds which I think will happen- I'm assuming your buds aren't "caked" with mud. If I remember correctly you are supposed to change the water every day gently refilling with warm water. The warm water softens the trichs and resin so that the "flush" doesn't break any off. Since THC/resin is not water soluble, I would think after refilling but before the water cools off it would be possible to move the buds around a little to wash some dirt off without losing the resin and trichs, but I don't know for sure.
I had planned to try it but did not. I have some buds where some of the leaves that intertwine with the calyxes had dried out and so I had dried leaves too small to manicure mixed in with the buds. I would think water curing those would have been good but I didn't do it. I was going to use some of those little plastic containers that a quart of blueberries or lb of strawberries come in at the grocery store, put the buds in there, and hold it down with a plate. Anywho...
There are threads on the forum with pretty good instructions.