I used Silicone spray on the valves in the old trailer to keep the seals from sticking. They were readily accessible. The new trailer has them stuck way up in the covered "basement". IIRC somebody ...
Yes that's we're talking about. My old trailer had the valves at the end of the drains, so I could easily spray the rubber O-rings with silicone. The new one has the valves protected up in the covered "basement" of the trailer.
And yes, you just dump the oil or Thetford Drain Lube into the toilet or sink. The sinks have a trap underneath, so you will want to put in enough to overflow the trap and get down to the tank.