Re: spit n polish

Try and find some really small steel ball bearings.
Count them as you put them in the tank!
Add some vineagar if the inside of the tank has gone green. Put the cap on and shake the tank vigourously horizontally and vertically.
Leave it for a day to let the vineagar work. Then shake the tank again before pouring the vineagar into a plastic vessel.
You will see from the colour of the vineagar how effective it has been.
If its anything else thats inside the tank you could use old paraffin & the bollies or even petrol.
Wash the tank out with hot water & washing up liquid, rinse and allow to dry.
Hopefully you should have a clean tank.
As for the outside of the tank have a look at chrome cleaners in a auto accessory store.