I have only done 5 of these types of floors . They all were sealed and waxed prior to my service call. I used orbital machine like the square scrub with a SSP pad and plenty of soap and water. These floors were at a hair salon. They moved everything including washing machines which was caked with salts etc.They all came out clean. If you don't have this type of machines then a 175 will work just be a lot slower. Bring with you a few different pads see which works best( don't kneel the machine trying to get out a spot that refuses to come off it's always best to just tell them it's a stain ) . You can always try a small hidden area see if it cleans if it doesn't then stop tell the customer it won't come clean. Everybody eventually comes across a trashed floor best to walk than be the guy buying them a new floor. Sometimes the epoxy just needs to be redone.
Legarri is just a small reseller of elite Crete products relabeled.If I did decide to do epoxy I would go to leggari products and learn to do it using their methods. Their YouTube videos are amazing. ps very nice photo.