Cleaning gas tank?

[Downlow2xfo]

So I've been workin hard trying to get my 65 stepper back on the road after digging it out from under some alabama pines where it sat for 20 years. Got the motor running and got some tires on the wheels I freshened up but now I got to get the vitals right. I pulled the tank yesterday to dump the 20 year old gas and the sending unit was roached. Got one coming in the mail but I still gotta get the trash and junk off the sides of the tank. I was told put a chain in the tank and shake it around? What methods have you guys used?