Here is what I do.
First, I make sure I get quality PG/USP. I like to use what they call kosher PG/USP. I get it from High Desert Vapes.
Next, I just warm it up, add the oil, stir until they mix well. Keep in mind, I am using clean, high quality, alcohol concentrates. That usually does it for me, they stay mixed really well for the first week or two.
You can add a drop or to of that EJ mix and supposedly it will help it stay mixed longer. Homoginizing can also help it stay mixed longer. For me, I don't have a purpose for any of that.
With the right vaping equipment, it isn't going to last a week!! I just mix enough for up to a week's worth of vaping. With the wick type top coil units, the wicking can cause the oil to separate more quickly unless you take the extra steps I mentioned. The top coils are pretty much ancient technology, as well as the cartridge type. You like KangerTech, you want to try the whoop? $50 should get you what you need. Well, $70 with the battery and charger. This is what I use
http://www.vapordna.com/Kanger-Subox-Nano-50W-Starter-Kit-p/nsubox.htm
I like the larger square 0.5 ohm (sub ohm) coils for cannabis oil. For e-ciggs I like the 1.5 ohm coils.
Flavoring, PEG400, I have a lot of information on my blog. I like organic, natural flavorings, which I also get from High Desert Vapes. Flavoring will mask the smell when mixed correctly. You can blow the vapor in someone's face and they would have no idea it is cannabis oil.
If you do try the KangerTech SUBOX Nano kit, you can use an oil mix that is thicker. I can have my solution so thick that the expando and buzz is too intense for me. I like to hit it more than once or twice! The KangerTech Subox Nano will work best when using PEG400, and flavoring to mask the taste. The reason why is this unit can handle thick oil and PEG400 is very thick compared to PG/USP. Most tanks can't handle the thickness of the PEG let alone straight concentrate.