[BlueRidgeGreen]

I always seal natural stone before I grout.

You can also very slightly moisten the surface of any tiles you are about to grout if they are still drinking a bit to keep the urethane from bonding immediately to the surface.

Once urethane is left to lock into any porous material, the haze can be incredibly difficult to remove ....completely.

Very small areas at a time as you are learning.

IMO.....the trick is keeping your joints full, consistent, and pretty, while making sure you have removed all your urethane haze.

I switched from my big microfiber sponge to smaller (about 3x5) and stiffer microfiber sponges.
The microfiber rags work well.....but with the sponges I avoid all the folding and tail flopping, and I can reach back to my buckets, rinse, and squeeze them dry really fast.