The video that L473ncy suggested regarding GBB basic maintenance should probably be stickied somewhere on ASC.
Personally, when I first get a hold of a GBB, I clean it before lubing it up. A good example of why you should do this is my Army MEU (look up my review and the attached pictures) - that grease between the loading muzzle and BBU is very likely not a good thing. Another example of why you should clean a GBB before lubing it is my used KJW M9 - the previous owner or two probably never dismantled it for cleaning, as there was a thick layer of black goop all over the internals (it was worse inside the internals in the frame) that desperately needed to be cleaned off. Adding more lube on top of the grime would have just made the grime loosen up and allow it to work its way further into the metal of the internals.
Anyway, regardless of the condition that your first GBB arrives in, you will likely see a slight increase in efficiency if you give it even a half decent cleaning (the slide rails are the absolute minimum). This is especially important if you're running a single stacker, i.e. a 1911 or variant, but regardless, a proper cleaning/lubing will most definitely allow for a more satisfying shooting experience with any GBB. And yes, there is such a thing as too much lube.
Originally Posted by m102404
just a tip to add...when you have it field stripped the hammer will be cocked, and you WILL be tempted to press the trigger...DON'T. It's never a good idea to let the hammer fall and strike nothing but the frame/innards to stop. It's a quick way to bash bits/parts.
And amen to that.
Edit: whoops, just realized that the topic was started a while ago. Holonite: go with RC lube. I believe the stuff I use (don't have the bottle with me right now) is for RC shocks, but I may be mistaken. Just make sure that it is truly 100% silicone oil, as a *something-something* chemical is really bad for the rubber seals in any GBB. I find that the thicker lube (as for RC shocks or whatever) works better for the moving parts of pistols, as lighter weights of oil tend to slop all over the place when firing - not good, because your parts will run themselves dry again in a shorter amount of time.