I use SEM spray in liner all the time. I used to use my Rocker Shutz gun, but I just sprung for a SEM gun. Haven't used it yet.
Stay away from the brush / roll on stuff, no activator, no UV protection, crap!
Its not Linex or Rhino. But its about 500 times better than Herculiner, Bondo brand, or one of those types.