Hi Lewis,
in my experience I didn't find washing & lube didn't make any difference (as far as I could tell), there's no harm in trying.
There's afew different lubes I've heard being uses, wd40 being one of them.
Some people just lube, some wash & lube, some put a very light coating on some put lots on. The main thing is to see if it actually works for your rifle, allthough some say it's more of a psychological thing.
Some people even say that lubeing there pellets made there groups open up.
So in answer to your question..... Depends, test & see :-) .
Mark