Wow! sorry for the late reply Jason.
Our spun domes came with coarse spin marks form the forming process; so to get mine to a similar finish as the real ones had, I sanded it with a palm sander as well as by hand. I think I started with 150 or 220 grit, then brought it to 360 grit paper. Once I reached that point, I hand sanded it with red scotchbrite pads. That gave it the the smooth-but-not-polished look that the real domes had.
Now I'm only basing my dome's look on the condition of the original domes as they existed when they were all renovated in the ILM modelshop for the prequel films. I couldn't say how close they may or may not have been to their original finish back in the 70's for New Hope. There have been decades of who-knows-what had been done to them. I tried to match mine to the dented New Hope dome that I had to hammer back in to shape in 1999. To smooth out the hammer and dolly marks from my repair, I used the same method as I mentioned above to match the repaired area to the surrounding dome. I think all-in-all it blended in pretty well with all the other dings and scuffs on Artoo's noggin.