When I did them I ran both lines to a 'T' fitting then to a single fill line so I only had to fill 1 line to my desired pressure thus equalizing each bag the exact same.
The only problem with that is uneven loads.
It's not THAT much of a concern, and it was how I was going to run them, but if you do have things uneven, the self-equalizing kind of works in reverse.....all the air takes the path of least resistance. Push down on one bag, it tries to go to the other.
Like I said, not THAT big of a deal, but it was something I kept in mind with this.