The oxy soak is a good tried-and-true method for removing labels. For whatever reason, Vinnie at Russian River uses some sort of NASA-developed super adhesive on his bottles because nothing short of a razor blade scraper and acetone have ever worked for me on Pliny bottles. Followed by a soap scrub with a green scrubby.
At 500ml (about 17oz) they are right in between 12oz and 22oz bottles, and for me, the perfect size. When I get 5 or 6, I'll do them in a batch, and it takes about 45 minutes of elbow grease to get it all. Pain in the ass!
I don't know what anyone means by "plastic" labels, but if they mean the slightly metallic-backed labels used by Jamil Zainasheff at Heretic (for example), I find they peel right off if I fill the bottles with hot-hot water from my tap. No fuss and no residue, though there is usually a straight line of sticky right where the last part of the label comes off, that removes easily with a 2 second soap scrub with the green scrubby.