Mixing is great fun and not difficult even for a clutz like me!
A few tips I learnt the hard way:
When you're buying needles for your syringes get at least one wide diameter needle (a lower gauge I believe) as VG is thick and just doesn't play ball with thinner needles. I would suggest a particular gauge but I'm not sure myself as I'm still struggling with my thin one (hence this tip lol).
Also I would recommend getting needles that are reasonably long so you can easily suck the liquid out of bottles as they get emptier.
Have something to stand your small bottles in (your flavours and your bottle that you are making your liquid in) so they wont accidentally tip over during mixing.
Hope this helps