Just for future reference, I do add more vinegar to the dye if I am handpainting. The yarn won't be soaking in the hot water vinegar if it is painted. I typically use this formula for handpainting:
1 cup hot water
1/2-2 tsp dye powder (depending on the color)
2 Tbs vinegar
I usually have plenty for 3-4 colors on a 420 yd skein of sock yarn.
I don't really think you can hurt the yarn by adding too much vinegar, so I put it in the soaking water and then again in the dye.
Does that make sense?