You'll find this spread talked about in the following threads as well:
Spreads
http://www.tarotforum.net/showthread.php?t=59210
http://www.tarotforum.net/showthread.php?t=46027
http://www.tarotforum.net/showthread.php?t=17651
Thoth forum
http://www.tarotforum.net/showthread.php?t=58926
You might bring up your questions in one of the "Spreads" threads also; it might reach other people faster than in here.
Personally, I find it less difficult to interpret than positional spreads, because you only have to go as deep as you want to. It's my favorite. I'd say it's effective - but not *necessarily* so; even the Golden Dawn material says it's not *foolproof*: "Find the Significator...Tell the Querent what he has come for: if wrong, abandon the divination. "
So, practice and look for meaning in stages. First, just turn over the four piles, and interpret the pile meaning in terms of the card showing, using dignities to strengthen or weaken. Leave it there. Then, find the pile with the significator, and add that *focus*. Later, add the *middle* card/s of that pile as the outcome (via card counting). Check for a majority of a suit, (weakened or strengthed by elemental dignities), and give the Book T meaning for that. Then check for 3 or 4 of a kind. These are all relatively simple things to check in isolation, without being quite as overwhelmed in putting it together as the counting and pairing. Then, when all those factors come easily, the counting and pairing will also be easier, because you'll know they take place within the *context* established.