@NU_FTW - Some of your reasons for choosing by volume are the same for me, even though I don't do the quantity at a time that you do. For example, I recently made (5) 50mL bottles of different recipes for the neighbor, and also (2) 50mLs of different ones for me...at the same time, in 1 mixing session...assembly line method like you.
I had each bottle labeled and marked already and its recipe card in front of it, in a row, to avoid mistakes of putting the wrong flavorings, wrong amounts, etc. in each of the 7 bottles. Some recipes I was making took some of the same flavorings, so I did those first...measuring out the right amount for each one and squirting it in each of those mixes. To keep track of what I've put in what bottle...I always put a little check mark next to that ingredient on the index card, when I put it in the bottle. Did the same thing with the rest of the flavorings, then shot the plain PG in each bottle up to the specified mark. Next came the nic for each of the 7 bottles, and finally the plain VG. Went like clockwork doing it that way. No way that I can think of, that I could've made those 7 different recipes at 1 time, without either having 7 scales and done a lot of taring, or...used just 1 scale for making each of the 7 recipes one at a time.
