Recommended palm sander techniques?
I really think a palm sander is the wrong tool for this job.  Palm sanders are great for finishing with finer grits but lack the power to remove layers of paint quickly. The siding job you are starting would go a lot faster with a 5 or 6 inch dual action (DA) sander with prepunched velcro backed sandpaper disks. There are several nice ones for under $100 and buying disks in contractor packs is a good value. I have two Ridgid 5 inch DA sanders and have used and abused them for years. I think HD sells them for about $70.