Looking through the MSDS on it, spraying it on with a gun would be about the same as spraying paint. Nothing overly toxic about it. Most of the chemicals used in it are harmful at a level that would be controllable with a very well ventilated area, or spraying outdoors. Gloves, respirator, and eye protection.
If using a respirator, you'd want one with a black labeled filter, for organic vapors. Some may have a gray stripe, which means it filters out particles also.
$150 for a quart. Well, one quart of bottom coat, and one of top coat. That will do 37.5 square feet according to them. While it says it does not hold up as well in an abrasive surface, I would skip using it on a mower deck. The top coat layer of that has silica in it. Granted, it's only 2-4 % of the total in the bottle, but still something to keep in mind.
I want to spray all the valleys on my roof with that stuff.