The H20 stuff is latex in a spray can, I don't recommend it for minis as it could peel off. It's more useful for coating styrofoam prior to spray painting it with normal enamal stuff. However, I had lots of bad issues even doing that. Of these, I had
1) Questionable coverage, as I still had bleed through that melted the styrofoam.
2) Water in the spray kept freezing up while spraying for long durations. This resulted in a paint foam that dripped onto my work.
3) $4 for a spray can vs. $5-6 for a can of brush on latex out of the oops bin at Home Depot. Even if I didn't have the above mentioned problems, didn't seem economically feasible for the time saving I got. Also the thicker coating the brush on latex provided more durability to the styrofoam.
Overall Krylon H2O, don't recommend it for any gaming uses.
Now if you want to prime minis, while you're at Home Depot looking for some nice neutral latex paint in their Ooops Bin for your next terrain project, go down their spray paint aisle. Check out Quick Color Spray paint, in a gray can. It goes for $0.98 a can and comes in Flat White and Flat Black. Just be sure you don't get the Gloss versions, the only way you can tell is by the sheen of the cap color. I've been using these for years and have had no problems.
Also look for Krylon Camoflage Colors, they go for about $4 a can and come in Dark Green, Black, Khaki, and Olive Green. They are very flat and good for primer or even a quick base coat.