Hello from Athens as well
If you are using the LGB style brass tracks I would stay away from putting any oil on them , its just going to make things worse. I also look forward to see some pics of your train and to read how these antislip rings performed. many years ago i put on the western train something like 8 western wagons and on the flat it pulled them without any problems. On the other hand when i set up outdoors my 4052 with just 2 red passenger wagons it was struggling a bit ( and I was using a JUMBO LGB power unit !

) when at an angle . The weight that clip under the wagon are important to have.
The 4375 power supply was adequate as well when compared to the JUMBO unit ( there is a limit of power supply to the playmo motors which must not be exceeded with the JUMBO unit ) and mind you this comparison was made on a 40m+ total truck length (very clean as well)