Nation,
You can never go wrong washing your pellets. As Saltlake mentioned above, there are release agents, which is kept kinda secret on what that stuff actually is. If I don't know what it is, I want to get it off.
The general consensus is that it can't hurt to wash them, and get that release agent off of them. Whether or not lubing them after washing increases accuracy, will depend upon the projectile as well as the barrel. It most definitely keeps the accuracy up in the gun for a longer period of time between cleanings.. At the very least, you got a clean slate to work with, if you decide to lube them or not. I've found that every gun that I have, there is no decrease in accuracy after I have lubed my pellets, pretty much in any gun.
I'll leave you with the video that Saltlake mentioned above, I also have videos on all kinds of pellet culling, for the competitor and the accuracy demanding individual.
https://youtu.be/b_9fP1z8D08
Tom Holland
Field Target Tech
Fieldtargettech.com