Multiple Aneroses?

This isn't my first foray into the world of Aneros. I had a Helix Classic before, but never got to the Super-O. No issues with insertion/removal or psychological hang-ups about the "back door," but I ran into other things - water-based lube drying out, scratchy P-tab, unable to get enough mobility and involuntary contractions. As such, I didn't get enough practice using it, and eventually pitched it during a move.
After reading stuff on the forum, it seems a lot of Aneros users collect / try several different models. I'm not sure if I need a smaller or larger model. I'm fairly short in stature (5'8") but there isn't an updated silicone version of the SGX. So I've decided to revisit prostate massage and placed an order for 5 different Aneroses: The DeVice, Helix and Eupho Syn, a Progasm Classic, and a Maximus Classic. This should be quite a range of models to experiment with.
I still think I have the potential to get wired for prostate pleasure. I'm aware of prostate feelings leading up to a traditional orgasm, and occasionally at other times. Hopefully the new silicone models (DeVice, Helix Syn, Eupho Syn), with their redesigned P-tabs and resilient materials, will be a little more comfortable.
So some questions while I wait for my order to show up:
- How do you know if a massager is too large or small to hit your prostate in the right place(s)? Or is that a matter of experimentation? In reviews, some suggest smaller models (SGX, Eupho) are more mobile and provide better stimulation. Others suggest larger models are in constant contact with the prostate gland and provide a more aggressive massage.
- Other comments suggest that the model is less important than the skill of the user in controlling the motion of the device, achieving involuntary contractions, etc. Any recommendations on how to learn this in my upcoming sessions?
- What's the right amount of lubrication? I suspect that in the past I may have used too little.