Well IMHO for small batches any kind of heavy duty or long mixing is not necessary; < 60ml or below, now then if your mixing up a gallon at a time, there are blending mixers similar to commercial paint mixers that will agitate a container at "X" number a times a minute.
That being said this is for commercial candy mixing, etc., and the cost is ridiculous for home use, after all these elements will blend:
PG
VG
Flavors : Various chemicals and extracts already suspended in PGA, PG, H20, etc.
PGA
All of the above blend rather well and with little or no vigorous agitation...
