I can understand why land owners would shy away from allowing strangers to shoot on their land, definitely a valid concern; but I think if everyone are willing to work together things can always be worked out. Here's a few options you might consider:
Get an umbrella insurance policy that go over your home owners policy, ask your agent about. You can get a few million dollars of coverage for a few hundred dollars a year I think. Now you can inturn pass that cost to people who want to help you with your hog problem. If you only charge $40 a person per day to hunt on your property, I'll bet you will have hundreds of people linning up trying to get in on the action. They are charging people $200 - $500 a day at some places.
Now designate specific areas that you will only allow people to hunt at, where hunters are taking shots from an elevated location and there are adequate back stops for the bullets, there by minimizing the chance of your neighbor getting shot. Maybe put up some makeshift tree stands.
I live in San Diego ..... we can't even shoot squirls out here. If you make it affordable for people that live outside of Texas to come over and shoot, I will bet the hogs would be endangered pretty quickly. I have 3 rifles, 2,000 rounds of ammo, and have nothing to shoot at.