if you want to add grease buy this one:
https://www.amazon.com/s/ref=nb_sb_...&rh=i:aps,k:general+transmissions+grease+ep00
the best way to add grease in your transmission is to put it through the brake lever.
there are some video in youtube for the RS800 that show you how to access the brake lever.
https://www.youtube.com/watch?v=grZPhUMnrYE
Again if you did not loose so much grease (less than a pound) I would not try to add more.