Definitely go with Rollers. We do that for our production boats even because it gives a nice "textured", non-reflective finish. On boats that we spray we even go back over them with a roller for the textured finish.
For adding sand, roll on one coat of paint, then while it's still tacky sprinkle sand on it LIGHTLY.
After that coat dries go back over it with a second coat of paint to completely cover the sand.
Good luck,
Kirk