Slicing - Illum 40k credits in 10-20mins
Once you get to at least 340 in slicing head to the planet called Illum (lvl50 planet). Can go as soon as you have ship access, when there take the speeder path to the warzone area of the planet.
The warzone has no spawned mobs but there are resource spawns everywhere around the map, run or ride from north to south around the battlefield and collect them.
In 15 minutes I collected 28 lock boxes which had between 1-5k credits each and 2 epic mission schematics.
Red Dots: Slice Boxes
Yellow Dots: Scavenge Debris
Enjoy while it lasts!!