+1 on HF bulk walnut media. The only way to go. I think my whole tumbling set up with: HF tumbler; a 25lb box of walnut media; and mineral spirits cost me $75 at HF a few years ago. I then went to the dollar general store next door and bought a bottle of Nu Finish and two 4 qt colanders for less than $5.
Pull a 20% coupon from the paper and get the media real cheap.