I'm one of the most experienced advantage slot players in the US. I've had 3 interviews on GWAE. I probably know more advantage slot plays than anyone out there. I used to teach it quite a bit online but got tired of idiots insulting me and expecting me to keep teaching them how to make money. I started in 1996 when the first big wave of exploitable slot machines hit the US.
There is an Australian named Peter Liston that has a book out called Million Dollar Slots. Apparently, Australia and New Zealand are permeated with highly exploitable Mystery Progressive slots. Liston made himself a millionaire playing them. They are pretty easy to analyze if you have the knowledge. We have Mystery Progressives in the US but as a whole they are not nearly as exploitable as the ones in Australia/New Zealand.