Shower – How soon after sealing grout can you use a shower

All you need to do is leave the grout to dry before getting it wet. The instructions should tell you for how long. As you and others have pointed out drying and curing are separate things.

While you can use the shower after the grout is dried you may need to leave it for a day or two after it's cured before sealing. You don't want to seal any moisture in.

It sure looks like you did a beautiful job on your shower, be a crying shame to see all that hard work ruined with stained grout. The glazing agent in the grout needs 8 to 10 days to harden completely. I suggest that you tape up some poly to protect the new grout if you really need to use the shower before the prescribed cure time. A few days of inconvenience is definitely worth not having to scrub and look at stained grout for years to come.