I like to use a stiff bristle nylon brush to knock everything loose off the sides and shop vac all of that stuff out. Then fill it with water and add citric acid. It takes a lot more citric acid than you'd think but it'll pretty much dissolve it all away. What's left can easily be removed with light scraping. The final step is to take a magic eraser (unscented) and wipe all surfaces to remove whatever haze might be left. I know
@Adam has been doing this a lot recently and he might have a bit more info but that's the route I've gone in the past.