I use Feliway and it doesn't stop the spraying. When a cat pees in the litter box and covers it, there is no odor as the litter is controlling it. When they spray, the urine is just there in it's raw form. Seriously ... cats do not have a separate urine source for spraying and peeing! It comes out of the same hole.
Spraying is a natural instinct! If a cat decides to do it, it will spray! Plain and simple. You either deal with it or ... you don't have a cat. IF a cat is spayed or neutered prior to sexual maturity and kept inside at ALL times as an only cat, then they may not return to that instinct. But, if you walk your cat outside or have other cats in the household, the spraying will be there due to territorial issues and the smells from another cat.
This is why SO many cat owners prefer their cats be indoor/outdoor cats. If they can spray to their heart's content outdoors, they generally will not spray in the house. Raiden is confined to two walks a day and sprays a lot -- the shrubs all smell GREAT, however, in the mornings when he wants his walk and he has held his pee all night long simply to spray on his morning walk, he will, at times, find a spot to spray in the house. I keep a black light so I can check daily the areas he normally uses and I haven't found anything lately. That's not to say that I haven't seen him walk up, turn around, lift his tail and I scare him out of there before he has a chance to spray.
You need to try and make these spraying areas as inconvenient as possible. But, they will simply find another spot. It's aggravating, I know, but if you have a cat, you have to deal with it.