I forgot to mention....bag the powerwashing idea for this problem. You could powerwash until the cows come home and you'll get nowhere fast, a hot water powerwasher may help...but it probably still won't do much. You could use a belt sander to get some of the paint off, I've done this when a deck had a major peeling problem on the deck boards and it worked pretty well. It's a job and you still have to use a solid colr latex stain (3 coats) to get a quality finish. I'd only recommend this for the posts, not the structure. The posts will still be marred by the sanding even if you're good with a sander.