Grit is just small rocks that take up space so your soil doesn't hold as much water. Usually sold under "Chicken Grit" or "Coarse Sand". You could substitute for pumice if you wanted.
Turface holds a medium amount of water.
Pine bark fines have random water capacity between medium and very high. They should be the same size as your other components (1/8 inch). Some people don't like pine bark because it breaks down too fast and you have to repot sooner.
You also need some complete fertilizer since bonsai soil does not provide nutrients like normal soil.