When making mixtures of viscous liquids and water (e.g. 50% glycerol), make it up in larger volumes and the room for pipetting errors decreases.
When pipetting viscous liquids use reverse pipetting techniques.For
larger volumes use a serological pipette and again, reverse pipette it
(e.g. to pipette 4 ml, suck up 5 ml and dispense, leaving 1 ml behind).