Good points!
Yes, in my opinion resistance is a product of our attachments. And our attachments are beliefs basically. Lets take the belief "I need women to be happy" for example. If we have that attachment, we need to to be aware of it first. And we get aware of it when we say the opposite, positive belief to ourselves. So if we tell ourselves "I'm completely happy by myself", the attachments come up as a tension in our chest/stomach, as a negative emotion. Thats resistance.
So, I think resistance comes up when there's a clash of opposing beliefs.
Letting go of your attachments will release resistance too since there's no clash of beliefs anymore. And if you release your attachments, you are indifferent since you are not attached to anything anymore and be free. This is the best state of being to create and manifest new things since you allow things to just flow.
You're right about certain states where visualizations are best to do. He also recommends this. Like I wrote, its called whole brain thinking where your brain hemispheres are aligned and you are in very deep state where quite no resistance comes up. I see it this way: If you go into such a state, you go behind all your attachments and limiting beliefs. You just pass them to a point where you can write your new beliefs/life on a "blank paper".
If you do a visualization right away in your "normal" state the beliefs clash against the limiting beliefs you already have and therefore resistance comes up.
For letting go of attachments/limiting beliefs he suggest doing EFT. You say your goal out loud to yourself, for example "I allow myself to have an abundance of pretty women" and then the first negative/doubting thought that comes up, you write down and release all the emotional baggage of it with EFT until it feels neutral. Then you say your goal again and write down the next thing that comes up and do the same. And so on until you feel neutral/care-free about your goal.
I do a lot of "Holistic Releasing" lately which I consider to be absolutely fantastic. Its a newer thing from Hale Dwoskins, creator of the Sedona Method and I think its really awesome. I will write a post about it today