Down here where the humidity is continuously >85%, 'bout all I use is dry corn. I have tried corn gluten and it tends to gum up the slinger because it absorbs the humidity. I do throw a little bit in my roll bbls though.
This past deer season I tried a small can slinger with soy beans. The deer didn't seem to favor them as well as dry corn and they are a little more expensive. At the CO-OP this past season, a bushel(56lbs) of dry corn was $8.50.
I have a friend that has a friend that works at a local peanut processing plant. The trucks pull in over a grating to dump their load of peanuts and what spills over the grates he sweeps up and keeps. They make their way to me and I sling them out by had for the deer/hogs. This past season I fed 14 bags at approx. 60-70lbs each.
I also get sweet potato culls from a farm just across the line in Ala. He sells a 1000lb box for $40. The deer and hogs absolutely love 'em.The ear corn is $60 per pick-up load.--- pruhdlr