The process of re-grouting consists of 4 steps:
Remove and scrub out the old grout, using a grout saw or grout scrubber. In some cases (for hardest lines) we use a rotary blade grinder.
Fill up joints with new grout spreading new grout diagonally across the joints, packing the grout firmly and deep into every joint using a squeegee or rubber grout float.
Wipe to remove the excess grout with a special sponge.
To finish we clean the tiles from remaining residue of grout using a dry cloth or paper towel.