I think I'll try the grapes also. I've heard of it before, never tried it.
To the OP - no, I don't wash frozen fruit.
Here's my recipe for a wonderful, thick smoothie:
Place in the blender
1 ripe banana
1/2 cup orange juice
1/2 cup frozen blueberries
1/2 cup frozen peaches
1 cup frozen strawberries
1 cup white grape juice from concentrate
blend
very thick, very sweet, very delicious.