Let's deal with this in 2-parts: (1) buffing/restoring the paint (2) buffing and protecting the aluminum.
The paint:
Glad to hear it is in well-kept condition. My A8 was in OK condition, not great, when I buffed it at 170k after 5 years of ownership. Most damage was from previous owners. The Audi clearcoat is indeed hard as any search results will suggest.
I polished mine at the time with Megs 85/wool on up to Megs 80 with softbuff pad. I just restored a dark green 1996 A4 w/ 226k earlier this year w/ 2 passes of Menz SIP/cyan pad followed by 106FF/tangerine pad (the hood got 85rd/grey pad as it was a black S4 hood) with great results. Pictures of that job coming soon.
Your M105/M205 combo should work well. But, I would be cautious going with something as aggressive as M105 if the paint is in good condition. Always do a test spot and start with the least aggressive methods first.
The aluminum:
I used to run the parts for a local Audi dealership for 3yrs and talked w/ Audi US corporate about the "aluminum" trim as mine is in need of restoration also. Audi has confirmed for me, at least on my 1997 A8, that the trim going up the a-pillar, along the roof, and back down the c-pillar are in fact aluminum, but the strips at the bottom of the windows are of the chromed-plastic variety. No word on the rub-strip moldings, as mine are in good condition.
The thing about aluminum is that it needs to maintain some form of protective coating if you want it to retain a mirror-like shine. This is because of aluminum's affinity for oxygen. Bare aluminum will react with oxygen to create a layer of aluminum-oxide, thus creating a protective layer which prevents further corrosion -this is what alclad aluminum is, btw. Aluminum-oxide is powdery and dull -not good for great appearance finishes.
So, after buffing/restoring the mirror finish on any aluminum it needs to be protected. This would be in the form of continual application of wax, a clearcoat of some form. Or, what I was going to try: There is a company called Henkel which makes a product called Alodine. From what I gather, this comes in a couple different varieties: a more or less a intermediary layer to apply a final protective layer on top, and a clear product -Alodine 5700- that seems like you could leave as is for the final "lsp" if you will.
What needs to be weighed with this type of work is the cost of new trim versus restoring the old trim.
Hope this information helps you. And I would also be anxious in seeing the results/final writeup when done
I will be sure and get lots of good pictures and keep you guys up to date
