A friend of ours, and a long-time gardener taught me this trick to get the grit off of garden greens. Rinse the greens in running water, then fill a bowl with enough water to cover the greens and add a cap full of vinegar. (About 1 T per gallon of water.)
Let it soak for about 20 minutes (or shorter is okay).
Then rinse the greens to remove the vinegar and excess grit. Whallah! Grit-free salads!