Need suggestions for getting old gas out of tank

Simple method I used to use to get a little fuel out of a tank (for filling diesel fuel filters) is to stick a decent sized hose into the tank with a few feet sticking out... something garden hose size works well... and then pressurize the tank by sticking a blow gun into the filler hole while using a rag to seal the opening around the blow gun. Once the tank gets a little bit of pressure it will force the contents out through the hose. Won't get every drop but might get ya pretty far down. At least lighten the tank for removal. AND obviously you don't want to get carried away adding pressure to the tank... regulate your air into it. It doesn't take much to get a result