MountainDevil54, for the aging part and using mustard, it's not the mustard but the vinegar in the mustard or rather the amount of vinegar. Straight vinegar will do well but it can be a bit tricky and can go much further than you want way faster than expected. It's really dependent on the type of bluing you are trying to effect and even the type of vinegar you are using as well. If you do decide to use vinegar, I would suggest you cut it with distilled water to raise the PH to around 4.5. Most vinegar's are around 2-3PH and fairly acidic. This is still something you will need to babysit like a $50 steak on the grill. If you have experience with other aging practices/products and find you do well with them I personally would stick to it. Vinegar based products for aging can be just too unpredictable and quite frankly a major pain in the butt.