Emptying gas tank question

[Alex Hayley]

I pulled the gas tank from my truck to clean it out in preparation for a new engine. The tank is clean with no rust but does have a tiny amount of junk in the bottom. I have tried draining the remaining gas from all three openings(see picture) but cannot get the final quart, or so, out. This concerns me because I would like to wash out the inside. I was planning to wash it out with hot water and then alcohol or lacquer thinner. However, if I cannot get all of the gas out, I will not be able to get the water/alcohol/thinner out. So...what am I doing wrong when trying to get the gas out of the tank????