When I did my mesc tek, I followed 69ron's foodsafe outline. Except I used HCL instead of vinegar because it is not so clumpy, and instead of citric acid because the yield is more accurate -- in the way that the citrate molecules are situated so that the yield will look a lot bigger than it actually is, and I wanted to be precise in that regard.

Just use your head and always at least open a window and wear protective glasses when handling the hcl.