If you are using Grout Shield, it IS important to mix the full jug with one full 25 lb. bag of grout to get the proper consistency. You don't want to guess this. Even with water it's tricky to get the right consistency by guessing or "eyeballing" the amounts. The lighter colors are well matched so there is no need to "pre-mix" both bags of grout, DRY like in the olden days. The darker shades of brown can be a little more touchy as far as color matching different bags with different batch numbers. But there are alot of factors affecting all that that I won't get into. LOL
Also important... After thoroughly mixing (hopefully you have a Milwaukee Hole Hawg with a mixing paddle) let it slake (rest) for at least 10 minutes, re-mix then start grouting. The lighter colors like Alabaster tend to stiffen up quicker, 20 minutes or so, when that happens, just pull your mixing paddle out of the water bucket and remix as needed. It fluffs the grout right back up.
Take your time, don't stress, it should take you about an hour to fully pack all of those grout joints. The grout has a pot life of at least 3 hours or so. When the grout is dry on the surface of the tiles, and is still semi-soft in the joints, it's time to start wiping. Lots of water! Two buckets of water, at least, for rinsing your sponges. One bucket for the first rinse (dirty water) and the other bucket for the second rinse (cleaner water). Change out all the water for the final rinse or as often as needed.
First wipe. Focus on "shaping" the joints. You'll see what I mean when you start.
Second wipe. Clean the surface of the tile. It will still have a haze but don't fret.
Final wipe. Clean the haze off and let dry.
In at least 4 hours, or the next day, a dry terry-towel to buff any remaining haze off, (we use micro fleece hand towels from the auto store).
Here's another tip... If you are using a 1/2" drill with a mixing paddle, don't use the chuck key. Hand tight is plenty. That allows for quicker paddle removal.
When all is done, pour a big fat glass of HHWiskey. It's grout day after all.
Good luck and go for it!
P.S. I don't see a rubber grout float in the picture. You have one tho, right?