I have never heard of Neville Goddard, but he must be quite an authority about the use of imagination, since you are mentioning him among so many others of the field of self-help.
Personally, I got quite some results with imagination, but it was not about objective, circumstantial outcomes - rather my model of psycho-physical functioning. Long time ago I figured, if I could make myself feel like Donald Trump or Bill Gates, then I would not need their billions to justify that feeling.
Well, I got myself to the point where I could swear that those two gentlemen never felt that peace, harmony, and happiness that I did, because they belong to those things that no money could buy - others being true love and health.
So, with my imagination I simply persisted upon an ideal, blissful feeling all over my personal space, removing on the spot any resistance to it. I can only tell you the same what so many qigong masters have said, Allen: "If it's not simple - it's impossible."
Don't forget those masters of imagination - little kids. Do they need a "complex modality or technique" to suddenly become "Supermen"? If we had not kept sabotaging them with our "common sense", who knows how many of them would have become filthy rich geniuses. That SAME sabotaging unconscious voice is sabotaging our natural use of imagination. Yours is probably telling you: "Come on, Allen, smarten up, you know it can't be done."
Well, override that voice by persisting. There is no magic intensity of imagination - but absence of resistance to it that brings about desired results.