At our ranch we had a similar problem but the difference was the skunks came into our yard and then our two goober German Shepherds would get sprayed. They never learned. They would do it again and again.
As with you, killing the skunks did no good as they just came back.
So I talked with one of my dad's K-9 trainers and he said to put a shock collar on them and train them to not go near them. Basically the same technique as rattlesnake training.
I already had the collar so I gave it a try. It took some dedication on my part as I had to wait till we saw a skunk in the yard…..and the dogs did get sprayed but it did break them from going after skunks.
Friend of ours took his hunting labs to a place down south of San Antonio that had skunks and they trained them to not go after skunks.
If his labs so much as see a skunk they make a huge circle to stay away from them.
Think it might be better for you to skunk proof the dogs instead of the yard.
I think there is the same folks that do rattlesnake training over by Pfluegerville or Austin somewhere that also do the skunk training.
Maybe Agvet13 on here can help with who that is.

Shock collars and anticipated effectiveness on skunks. Also anticipated success rate getting collar on skunk.