Hi Mandalor,
I've read 3 of his books a while back and couldnt put them down, and he is well known for his work in this field. I believe he still holds workshops at the Munroe Institute founded by another pioneer in OBE methods the late Robert Munroe.

I have never consciously tried this method simply because I discovered Robert's method before reading William's books.
However I would not doubt for a second the method. Well worth trying.

Visualising the chosen area is good practice for the brow and of cousrse the longer you spend on this the more your body should slowly be relaxing and slowly every muscle will be totally relaxed but the mind still aware. These are perfect conditions to be practicing.
My only shudder is when I hear anyone putting a timescale on this. I've noticed that some will be expecting a result in the time frame given and if it doesnt happen they think they are doing something wrong when in fact all they need is practice and patience.
I hope you come back here and report any success if you try this method. Would be interested to hear.