Done plenty, but not alclad
There is not really any "magic" to polishing aluminum parts that have some "heft". I cannot comment on polishing alclad skins since I have not done it (yet). I can certainly understand the comments about overheating the thin skins. For me, the usual error is moving too quickly towards fine grit media. Make sure the offending scratches or rough surface finish you are trying to eliminate is completely evened out at the current grit size before moving on to finer grit. If you don't, you will have to retrace your steps when you go back to coarse grit to get rid of that one mark that won't go away. Most of my polishing has been related to show motorcycle parts, not aircraft parts. 1600 wet is where I move away from paper to the buffing wheel. Wheel time is small compared to the paper time.