I have used the 0.9% saline solution (wound wash). It does add a bit of "moistness" to the mixes I have tried it in. It also has the added benefit of acting as a flavor enhancer as well; much like salting food aids in better flavor. I do not automatically add it to everything I make, but if I can't get a recipe to quite pop, I will give this a try. It can also smooth out harsh edges of certain mixes. Use sparingly; usually only a drop, or two, is all it takes. I thank
@Slots for turning me on to its use.
Use only wound wash saline. It is sterile water, sodium chloride and
nothing else! Do not use saline for eyes, contact, or sinuses, as the almost always have additional ingredients which pose unknown safety risks.
Wound wash can be purchased at most pharmacies such as: Walgreen, Rite-Aid, CVS, and Walmart. Here is an example of one of Walmart's listings: Wound Wash. There are multiple brands and labels (including in-house branding). Any of them are fine so long as the ingredients are listed as sterile water, sodium chloride (0.9% or 9mg/mL... I've seen both) and nothing else. It always seems to come in a pressurized can, so I simply dispense about 10mLs at a time, into a small dripper bottle, and use that as my working product. Used in that manner; a 6 oz. can will last you years.
I have tried using distilled water, from 5 to 10 percent in recipes, during my early days of DIY. But, the popping and spit-back was so obnoxious and distracting, I could not tell you whether it helped with a moister vape. I abandoned this method after 2 or three attempts.
I do use EM occasionally in a few recipes; but I have never noticed it contributing a sense of moisture. YMMV
The other additive I have heard (more than once), that can help create a moister vape, is Inawera Cactus.
I have not yet personally tried this ingredient. Apparently, when used in small amounts, it will contribute a sense of moistness without altering the overall flavor profile. You will need to research further to figure out how small is "small."