Mixing by weight for a few months after using syringes for years. Some things that are helping me:
*VG: 100ml+ squeeze bottle (food dispenser)
*PG: 60ml+ squeeze bottle
*Distilled h2o: plastic dropper bottle stays in the fridge to slow microbe growth. Can also use the final containers' dropper while clean.
*Flavors: Everything is in dropper bottles, 2 dram dropper assemblies bought in bulk for WL vials. For the odd flavor with no dropper, I add it last with the finished container's clean glass dropper.
*NIC: GLASS dropper bottle, 30ml+. To minimize spillage/mess, don't fill past 9/10. Mixing for myself at 1-2mg, this lasts me like 2 months before refilling and keeps nic out of my kitchen sink from rinsing syringes.
Haven't had to throw anything away or make a trip to the sink as part of the mix process for weeks (besides cleaning empty bottles) and lovin it.
Also, if you're washing and reusing a lot, having a
uniform set of glass boston rounds and droppers is king: the dishwasher/and or batch hot-soak is your friend. Disassemble the droppers and put them in one of those plastic mesh dishwasher-cage accessories. (Pinching each assembled dropper until it smells clean is a time-consuming, water-wasting PITA)
15ml glass is almost too small to justify getting the supplies out or washing the damn thing, go for
30ml!