Type/brand shouldnt matter, as long as its USP grade and not industrial. I have some Wiltons brand, and some from "From Nature with Love". I like the FNWL brand better, absolutely no smell, and great vapor production.
As far as how to mix it, I would suggest looking in the DIY forum and looking at some recipes.
I made some
juice last night that is simply glycerin and a little Lorann flavoring, nothing else. No
throat hit, but the taste is good and vapor production is outstanding.
hth