Advice on Undercoating

[AU Doc]

Can anyone offer suggestions on a good undercoating for a car that will see lots of time on the road? I would like something that will stop the progression of any existing rust, and is very durable. I would also like something that requires as little prep as possible I realize that last part might be asking a bit much, but I figure ask for everything I want and then see where I land.

I've considered POR-15 because I remember the stuff being rock hard, but there doesn't appear to be much rust for it to bond to. I've also considered bed liner as it seems like it would be about as durable as it comes. I'm just not sure what sort of prep would be required or whether it will stop/prevent rust.

Thanks in advance!