Buy a low resistance (1.8 or 2.0) atomizer. Brand I don't think really matters, Joyetech, Smoktech, Ikenvape, whatever...
You'll also need a drip tip to top the atomizer. They come pre-filled with a primer so you blow that out into a paper towel then drip 5-7 drops to start. When changing flavors I just blow out the
juice, do a QUICK dry burn and put the new flavor in.
Search dripping on an atomizer in youtube and watch some videos, its really simple.