For the walls you ll have to spray on the sealer and wipe around with a paint brush or sponge to keep the tile and grout wet with sealer long enough to soak in.
Applying sealer to marble tile pre grout.
Apply the sealer to the carrara marble tile and grout by creating a film of sealer.
The spray on variety is the most common although some types can be applied with a sponge or brush.
Then grout using non sanded grout.
Marble sometimes gets circulary etches scrathed into its polished face with sanded grout.
Apply your sealer to the lines and joints of the grout.
Then wait 3 days minimum after grouting giving time for grout to cure and then seal the grout.
Then wipe off all excess until completely dry.
Step 3 application.
Let it soak in for 2 5 minutes.
Sealing the tile before grouting doesn t get you out of sealing it after grouting though.
Use an impregnating sealer.
If your tile is not glazed be extremely cautious when applying the sealant as it will absorb directly into the tile and will change the color and finish of the piece.
To protect your tile properly seal it a second time after the grout cures.
You can apply another coat of sealer on the tile too.
I would seal the tile before grouting.