Make sure you take your time to apply the spray, key to spray in even strokes from side to side extending past the tank, dont rush it. stop and look at your application and then you can see where you need to re-spray.. it takes two to three apps, depending on size of tank..
Please make sure all surfaces you DO NOT want paint on, are taped off, so nothing can seep through..you can't rely on newspaper only..use plastic even cardboard to help seal.
So far my betta hasn't been too affected by background paint..The tank is planted and filter, decor keep him occupied. Before him had other species (cichlid) :)