Uh, buckshot sucks rocks on hogs, but slugs work well. .30-30 ammo is usually either 150 grains or 170. I'd prefer the 170s, but it's not a big deal. Generally the heavier the bullet, the better the penetration
per caliber.
The OP was talking about Crossville Tenn., which should be brush country and steep hillsides. As mentioned, the terrain will drive the gear or the shooting distance. The .357 carbine will limit the engagement range the most, the .300 the least.
Couple of things to note: Check with the guide for a real recommendation as he should know the terrain. Unless someone here knows which part of the Cumberland Platau the property is on, we're just guessing.
Also, use tough bullets - hogs can get quite thick. And, the heart lung shot on a hog is a bit tricky as the heart/lungs are forward from a deer's. I always try to bust a shoulder with the bullet, either going in or coming out.
As regards handguns for back up, always remember that on snouted animals, the brain is between the ears, not the eyes. Shooting them between the eyes from a downward angle does little. I use a 9mm with Gold Dots and it works fine.
PS. Shot placement is critical.