The MWS is as we know an efficient design, as such it does not need a lot of lubrication.
Unlike crap GBB designs where there is a lot of excess venting / gas blowby which dries out the BBU/piston seal.
This is the reason lots of people run these on propane with great success.
Mags always need to have pressure inside to maintain seal function / lubrication.
As for servicing of mags - if they are leaking - strip them down, clean them out, check seals for damage and bloating, check all seal mating faces for scratches or debris.
Coat the seals in quality silicone oil and reassemble.
PTFE is not required / advised.
Gas the mag up like 50% and check for leaks.
Silicone grease the piston seal, everything else should be dry, or metal on metal lubricated (Wurth dry grease or gun oil)
If you are not using the gun for a while then had the mags with suspended oil gas.