Mix the grout by pouring the water in first, and then add the powder, and stir with a margin trowel. Mix to a smooth (like toothpaste) consistency, let sit for five minutes, then mix again.
Note: The thickness of your joint will determine if you can use sanded or unsanded grout. If the joint is less than 1/8", use unsanded; wider than 1/8", use sanded.
Wash down the tiles after small areas so the grout and film don't dry on the tiles. Leave the corners and edges free of grout since silicone will go there. Clean the grout out of the corners of the walls. Continue grouting other sections.
Wash the surface three times: First to remove the excess grout, second, wipe the surface with a wrung-out sponge dragging lightly, being sure to wring out the sponge after each drag, and third, buff with a dry cotton cloth to polish.