I wouldnt use tire slings. You are wanting to not only secure the vehicle, but compress the suspension somehwat so you dont have horrible body roll/bounce.
I carry 8 axle straps along with the 2.5" Yellow 10k pound webbing ratcheting straps availible at Home Depot pretty cheap.
Axle straps:
are availible in a variety of load capactiies and lengths, and make it easy to strap to rear axles, loop through Lower control arms, etc.
I also have a variety of cluster hooks:
that have R hooks, J hooks, etc that are meant to be inserted into the frame of the vehicle in the specially cutout holes in frame for just this purpose.
Having the right tools for towing REALLY makes life so much simpler!
And whatever you do, dont try to tow a dmax with a denali on a 7k trailer lol