Bad, I use the stopper instead of a needle for VG and I think it is much nicer, cleaner, easier than using a needle. VG varies in thickness, but I cannot see using anything higher than a 16 ga needle and 14 ga would be even better. Still recommend going to Walgreens and getting the stopper+syringe though.
"Rough in" VG is roughing in the percentage. I have a few 110 ml bottles I got for nothing. In these bottles I will put in 30ml of VG and then 70ml of PG (as an example). I then use that bottle for my cutting base. Depending on how the recipes goes using this 70/30 bottle would give me anywhere from 20% down to 5% of VG in the final mix. What the final ratio of PG to VG is in the recipe is of slight concern.
So if I have a 50/50, a 70/30, and a 90/10 premixed PG/VG bottles sitting around. I'd use the 50/50 bottle for "high" VG, the 70/30 for "med" VG and the 90/10 for just a touch of VG.
So I don't fret, worry, or concern myself with the final VG content and just think of it as High, Med, Low vapor production PG.
And with these bottles I also use the stopper&syringe so it is quick, fairly accurate, and non-messy.
(I have 6 of those stopper&syringe thingy's from Walgreen and Walmart, but like the Walgreen ones better because of the included brush for cleanin)