Best place IMO to farm BOTH Grave Wax and Fat Wax is "Flower Viewing Stage Idol" in Fountainhead. Right behind you is one of those super easy to kill blue piper guys and he's set up for a backstab. Just use a Posession/Wealth balloon and kill him repeatedly. If you want double the chance at items and double the gold, use Golden Vortex fan(and the Ceremonial Tanto will keep you not using spirit things.) This guy drops both, at good drop rates, and giving decent money and EXP too.