cleaning out recently painted tank

[prue1]

As I continue sorting out my rebuild I have come across another challenge. When I purchased my bike, the fuel tank was recently painted and a coating was installed inside the tank to prevent rust. this coating and the rust underneath it continues to foul my carbs (even with aftermarket fuel filters installed). I have read numerous posts as to removing rust, but I need to get this "coating" out as well.

Any suggestions that won't damage the new paint on the outside?

Thanks.