I'm betting the "bumps" inside the pot are mineral deposits ... so Callisto's method would work - or even just filling it up above the level where the sludge was and letting it sit over night. Then, you can use a green scrubbie and a MILD dishwashing soap to clean it. From what appears to be the "water line" I doubt the spout is clogged or coated with mineral deposits.
As for the rust around the rim of the lid - just use a paste of salt and oil to scrub it clean - wash with mild dishwashing soap, rinse, dry and give it a light coat of oil.
Of course to reseason it - you'll need to run a few pots of boiling water through it - until it doesn't have any taste - and then make a few pots of tea.
As for the rust around the rim of the lid - just use a paste of salt and oil to scrub it clean - wash with mild dishwashing soap, rinse, dry and give it a light coat of oil.
Of course to reseason it - you'll need to run a few pots of boiling water through it - until it doesn't have any taste - and then make a few pots of tea.