IIRC...as far as their OSF and OSB, they will show a VG% if there is any VG in it. If there's no notation of a VG %, there's none in it.
About sucking up the flavorings with VG in them - Don't try to actually "pull" the flavoring up with the plunger. Instead, insert the needle tip into the flavoring bottle, and then pull the plunger up to the mL mark you need. As long as there's a gap between the barrel of the syringe and the neck size opening of the bottle...just wait then for the flavoring to rise up to the bottom of the plunger. Air pressure and creating a vaccuum is what makes it do it, and it works every time. I never fight at all with even plain VG doing it that way.
^^^
Adding that needle size matters when the viscosity is thick. Typically I use 14GA Luer-Lok blunt tip needles for VG Heavy/100% VG liquids (and on some of my 30ml dispensing bottles w/LL caps I use to fill mod bottles/atty tanks, etc with). They can also be used to drip atty's, but I prefer to use twist top dispensing caps on the bottles I use for that.
Even easier (if you have syringes that can use them) is the all SS LLBT 12GA or 10GA needles. They typically are much longer (5"), but can be cut down easy enough if wanted with a roto-tool cut off wheel (IE Foredom, Dremel, etc).