I do think that if the hypnosis sessions have the same or similar goals as the subs, they can work like the old superchargers, where you align your conscious state with your subconscious one. Which may make subliminals more effective.
I also think that if you learn how to put yourself into a meditative trance-state where you merely observe thoughts instead of classifying them, subliminal messages may come through more clearly.
It is a really interesting state by the way. Imagine looking at a traffic light but not calling it a traffic light, seeing the colors and shape but not calling them by name. You just observe, completely open, this “thing” in your field of view.
I suppose that’s what it is like for children before they are taught the words. They just see things with complete objectivity and curiosity.