No idea about the perfect pushup, but the "expander" you speak of is a great piece of equipment if you got the "right" thing. That is to say that the resistance will be great enough to give you a real workout. I would say that you would probably want something that at least hits on the hundred-200 lb resistance if you want to get a lot out of expanders. Ideally you would be able to adjust from 10lbs up to a couple hundred depending on what you were doing. I believe they also used to be called cable or strands... so googling those may give you some interesting old time strongman results. If you wish, I can also provide some good places to look or get info.

I won't comment on the perfect pushup.