Invest in a Carboy Cleaner system.
Mine does wonders for stubborn stuff, and the vendor had an awesome giveaway here a couple months back.
Schöne Blondine Brauerei
Closed-System Pressurized Fermentation - the future of homebrewing today...!!!
“Simplicity is the ultimate sophistication” – Leonardo da Vinci
"A set back is the opportunity to begin again more intelligently" - Henry Ford