Yes, I concur, SG is really easy to apply and remove if you have a nice clean, well prepped surface like using the PC with Finesse-It II or PPCL.
I have not seen any objective data anywhere that applying AIO before SG or adding coat after coat of SG really improves how long the shine lasts that much - but it's not much point if you detail your car ever 4 months or less as one coat will last that long. I'm sure it helps somewhat but I would bet the law of diminishing returns applies in this case. If you read the instructions, Klasse even says the AIO isn't necessary if you are using SG on a new, un-oxidized finish (my cars are 4 and 18 months old - older cars like 3 years and more may benefit from the AIO if the car is detailed 3 or less times a year). In addition, I definitely don't think the AIO really does any good if you use a polish/cleaner beforehand anyway like Finesse-It II or PPCL.
Of course other opinions will differ but there is a web site (I forget the address) that did "The Wax Test" where they pretty methodically tested quite a few products. Zaino, P21S and Klasse all came out on top with not much difference in how long they lasted and they only applied one coat of Klasse if I remember.
It's really easy to go overboard on this stuff, but if you are having fun and have the spare time, have at it.