we had our cat neutered but it still sprays things outside...any way to make hime stop this?

If he is only spraying outside it is not a problem, and bringing him indoors will only force him to spray indoors,.

Take stuff he has sprayed on, collect them, and put them in one area, and let him spray there, be sure to wash everywhere else thoroughly with a hose. You won't be able to stop him, rather giveallow him one area to do his thing.

Don't let him outside.

Really, that's all that can be done. Cats spray to mark territory. When he has such a vast territory as the outdoors, he's going to spray. Give him less territory, he's much less likely to spray.

He's just marking his territory. If you want him to stop, keep him indoors.