So you tiled your backsplash. Did a celebratory dance, and settled down with a glass of vino. After pausing for 24 hours(ish...read the box!), it's time to GROUT! This is my favorite task, IMMEDIATE satisfaction. Tile without grout is like Chipotle without the Guac. Still tastes good but you KNOW it's missing something good.
I went with the whitest white the grout came in (Bright White) in an Unsanded grout. HERE'S the deal, SANDED grout is sturdier, good for large grout lines. BUT, there is sand in it, which when spread on my dear glass COULD scratch it. So that ain't gunna happen. Also, my grout lines were small enough (I made sure) to fall in the Unsanded category.
Grout can come in a pre-mixed container, it's a little harder to find Unsanded in premixed, so I had to mix my own - NBD. Make sure you mix enough for the entire backsplash, ESPECIALLY if you have a funky grout color. Grout colors can vary depending on how much water you add in each box.
THEN all I did was smear it everywhere (even my hands! = no photos), let it sit for a few minutes and use a sponge to GENTLY wipe the excess off. I went back a few times with the sponge getting rid of the after-haze...and VOILA!
I didn't ground the bottom line, I used a silicon caulk to seal it up. Pro tip: they put $$ silicon caulk in the tile isle, go to the paint isle for the cheap (and JUST as good) stuff!