I have some videos on restoring rusty tanks. I sure most of you are only interested in the sealing process. Check out the third and fourth video:

http://www.howtomotorcyclerepair.com/restoring-a-rusty-motorcycle-tank/

I also coated my tank recently using Caswell epoxy tank sealer. It is still too early to comment the long-term effects, but from what I can see, this is a very decent product. It’s quite easy to work with, has no obnoxious smell, cure quickly, and the hardened surface looks as tough as nails.

There is already a huge thread on this subject, but IMO, one of the most important things is to ensure a CONTINUOUS liner that COMPLETELY covers all contact areas of the tank, including the filler hole's neck and the fuel pump opening's lip. This way fuel can’t get between the liner and the tank, which is one of the most common failures. I used a small paint brush to put on a couple of coats on the tank's neck and lip.