I taped plastic protection all around the walls, architrave and skirtings up to 1m high using low tack masking tape as i used an floor buffing machine , then i used a degreasing cleaner, i wont mention brand names as most companies sell a generic degreasing cleaner ,this was mopped on to the floor and then i used a white 15inch white scouring pad on the buffing machine and then hoovered off the excess dirty water with a wet and dry hoover , the floor was allowed to dry out thoroughly and then the joints were lightly sanded with 120 grit sand paper which brought the grout up to its original colour ,the next step is to reapply new impregnating sealer, i chose Fila mp90 for this (other brands are available ) and sealed all the tiles and joints, this was repeated 3 times and the floor was finished using a clear paste wax which was buffed with a soft brush on the buffing machine
hope this helps
Gary