You can get a lot of obedience passively. Maid uniforms and slave collars can increase obedience pretty quickly, and you can swap them to a new maid once the obedience is high. Also, punishment and praising works really well, and a punishment + beating works exceptionally well, though it will backfire if their obedience is already high.
Loyalty is harder to build - praising or sex is the best way. It'll grow on its own day by day, but very slowly.
Make sure they're getting enough luxury for their grade, or both loyalty and obedience will go down daily. Slaves don't need anything, but even a Poor grade slave needs some nice underthings or some extra food.
Punishments and slave collars cause stress, so you'll want to stretch those out over days so they relax. Or just Sedate them.