I just use a bit of mineral spirits or denatured alcohol. Wipe on with a rag, wait 30 seconds (ventilated area, respiratory protection, blah blah), then i just use a razor blade to scrape labels and funk off. Its a zero elbow grease event. I'm not saying citrus based stuff or the MEK won't work, there's a million ways to do it. I'm just telling you what I did with materials available in my shop.
"This is grain, which any fool can eat, but for which the Lord intended a more divine means of consumption. Let us give praise to our maker and glory to his bounty by learning about... BEER." - Friar Tuck