If it just gets a couple quick wobbles while it goes up or down in rpm I wouldn't worry about it. Even if a ball on the training gear is slightly wobbling. From what you describe, I think your heli is running just fine.

I lubed my dampers with vaseline when I installed originally and during maintenance but most of it seems to get squeezed out installing the feathering shaft. Tri-flow or some of that silicon dielectric grease you can get at auto parts stores will work as well.

I've seen t-rex helis do the same thing so I wouldn't worry about that. I used mine with the plastic stuff forever and flew fine for me. I've got a friend that flies a nicely equipped trex, I let him take my MT up when we get together IMO it makes his flying look more precise and smooth.

Biggest contributor to the shimmies I have seen with my MT is the tracking. If it is even slightly off I think the spool up/down was worse for me.