What got me over the hump of consistently good guiding? I'll give you two answers--one long and one short.
First the short answer: Money. I bought a better mount and virtually all of my autoguiding problems disappeared.
Now the long answer: I struggled with a mount that was at the limits of its capacity for a little over a year. I had no problems with differential flexure or mirror flop since my camera is internally guided. Ultimately, what it came down to for me was that my mount, when loaded with 22 pounds of imaging gear, simply didn't track that well. There were shifts of 1-2 arc seconds in RA that occurred over time frames that were too fast for an autoguider to keep up with. I was able to make incremental improvements through adjusting the worm/wheel meshing, adusting the couplings between the drive and the worm, making sure the mount was well balanced (meaning a few ounces East heavy), etc., but I never got the results I thought my scope was capable of. FWHM numbers simply weren't where I wanted them to be. Then I received my ridiculously expensive, very high quality mount and all my guiding problems went away instantly. When using my old mount, I typically got RMS errors between guide exposures of 0.4 pixels to 0.6 pixels with my refractor (1.2 to 1.8 arc seconds). I put that same scope on the new mount, and the first night out--a night of particularly good seeing--I got RMS errors between guide exposures of 0.02 to 0.1 arc seconds. The high end mount took away the struggle.
Can you successfully autoguide with a mid priced mount? Sure. Can you autoguide well with a mid priced mount? I never did, but I have seen plenty of evidence that others do. How can you get truly good autoguiding results with a minimum of effort? Buy a better mount and don't overload it.
Yep, I figured that a better mount is the ultimate way to get over the hump - I may do that eventually. The CGEM was supposed to be my better mount but after I bought it I realized that it's tracking accuracy is really no better than the LXD75 I sold although I had to tinker with the LXD75 for a while to get it decent results. It is a much better mount in just about every other respect though (very solid, good go to's, nice software). I learned after the fact that I shouldn't expect low PE out of the box with a mount in this price range. I confess I was disappointed to learn that but I see plenty of folks getting good results out of this mount class and hopefully I'll get there (with a few frustrations thrown in to keep me humble I'm sure).