I did some slat repair in a ~20 yr old finishing building earlier this year.   So far it looks good.   It better though, it's not cheap and its a lot of work.

I used a product called Conkorite to fix the really bad areas and then put Armour Rock (epoxy + sand) on the slats around the feeders.

Both are Vanberg Coatings products and are available through Hog Slat.

Vanberg's website seems to be down currently.