umm there are a few ways
to disinfect it I think its 1 part bleach to 10 parts water
the white film unfortunately you will have to use vinegar, but instead turn the tank on its side, and let it soak for an hour or 2 so it has a change to dissolve the crap (might take longer I've had to soak equipment for up to 8 hours) I know from working with salt water vinegar will even pretty much everything if it soaks long enough. After you are done make sure you rinse it good
If you do the bleach (probably after) rinse it well and let it air dry for a day or 2 to make sure the bleach is completely out.
Unfortunately there is no easy sure fire way to do it basically its time and patience. Scraping it with a razor while the vinegar is soaking on it might speed it up.