OP, I’ve had similar experiences with my LGB rail buses. As far as a very slight amount of brass wear in the frogs, that’s fairly common. you will need to use your own judgment, I have had “expert resources“ , a certain Klaus, suggest using a touch of oil or WD-40 on the rails in order to reduce friction.
Some years ago, I have tried both WD-40 and very light mechanical clipper oil. I did this i hopes of getting tree sap not to stick to my rails. It was not the best decision. Both collect various gunk and debris and stuff from the air and eventually will need to be removed with a cloth. This leaves black streaks on the cloth, and may require further chemical cleaning with naptha, meths, or track cleaners.. OTOH, lubrication does work, and prototype railways use it. I will tell you flat out that if you have grades, it may be a very poor choice.