Tony: Here's my take on the grease issue; I don't own one of these engines and am commenting using the illustration from the owners manual-each "engine" will have only one worm driven shaft to drive them. The illustration only shows one "Grease" port and that is on the rear engine. There SHOULD be another grease port for the front engine as well; is the illustration wrong? You'll have to check the actual engine and ascertain that.
As far as actual grease, I like to use Lucas Oil's "Red 'n Tacky #2 obtained at any auto parts store or Wally World. A tube will last a lifetime. Get a small plastic grease injector applicator (Amazon...) and use that to inject some in each Grease port.
You've already taken care of the linkage oiling and the axle bearings which is a good start to maintaining your loco.
