not many use them now, when you buy them then wash them in warm water with some vinegar added this kills the fat that is in a new mop so makes it work better, you should wring them out, to do this hold the mop in centre with one hand then with other hand grab a large section of mop ends and wring them till damp work your way round the exterior of the mop till all sections are done, some people need to wring them out in 3 sections but if you have big hands 2 sections is enough make sure you always hold the centre if you try to wring them out using two ends then you can snap the string that holds all mop ends together.
in the early 60s window cleaners would use 2 mops one for removing majority of dirt then a clean one for polishing the glass but in the late 60s most window cleaners where using a nearly dry piece of scrim for the polishing part, today mops and scrim have been replaced by squeegees and microfibre cloths.