When I tune/conditition them I sand ACROSS the tongue, not with the grain (up n down the tongue). I learned that from Dick Kirby, I was out hunting and ran into him, years ago. I was in the parking lot sanding the paddle on my box call and rechalking it, He asked, *what the hell are you doing* told him I was sanding the glaze of the lid to rechalk it. He grabbed the call away from me and asked who told you to sand it like that? I said that what it said in the instruction, sand it length ways of the lid? He shook his head and said toss those instructions, they're useless, you never sand with the grain on a wood to wood friction call, the rails you sand with the grain, the lid you sand across the grain!! He then resanded the lid and chalked it up and said now play it. It sounded a heck of a lot better. Sanding it with the grain make for a very high pitched sounding call. Sanding across the grain creates a checkering effect in the wood and makes the call play a lot easier. So with a tongue call where you have a small tipped striker, you need all the help you can get to make them easy to play, sanding across the tongue creates that checkering effect and you can play them in any direction. I've sanded every box call, tongue call, scratch box striker, I've ever owned across the grain.
When I sand the tongues, I use 80 grit to conditition them, or a 100 grit if I need a higher pitched call, then in the woods I use just a fingernail file to scuff them up a bit to keep them play right. Don't sand too much, just enough to get rid of the glaze.