Sorry for the late reply Dan, the forum has been down here.
Use a very fine wet and dry paper, and use it wet. Rub down lightly. It should remove the 'gritty' effect, and leave the surface smooth. You might even get away without having to re-spray, but if not, then give a very light misting only. Check the thinning ratio - if it's acrylics, then Wayne is right, it's drying as it hits the surface = needs more thinner, but just a touch. If it's enamels, it's too close or too thick. Try backing-off a bit first, or, if required, just thin the paint a touch more, and practice spray onto some scrap - the wall, your car.......just kidding!
I have a feeling it's too close though, as this can cause bubbles in the paint as it hits the surface, which then dry as 'pebbles'.