Smaller say 100ml amounts for flavour/nicotine = syringe the mix
Moderate say up to 500ml you can syringe the flav/nic or weight then top up by eye/weight the VG/PG balance
Larger amounts 1ltr+ well you will be going some with a 10~20ml syringe, think I got a 50ml syringe somewhere
(obviously a 5ml syringe will be more accurate at dispensing 4ml than a 50 or 100ml syringe would)
All depends on how complex the mix - lots of flavours - syringe most likely for testing or small to medium qty
At least of the critical flavourings & nic
straight forward stuff with a couple of flavours in a moderate amount weight would suffice 500ml or more say
At least with a syringe you get the VG dispensed easily but depends on what you got to hand and how fussy & how much you are mixing
But shake the bottle very well you are using or with a long needle especially reaching the bottom you will pick up the sediment and more concentrated flavour & nicotine most likely