Use Panel wipe to remove the residue first, then the trick with the water, this will remove any oil residue, hot water filled right to the rim will remove any vapour ,then empty and dry out, final test before any work , use your nose to detect if anything is left.
If containers are sent in the post or by courier that have residue left in them many carriers will refuse to transport them,
so whatever you do, the tank must be as clean and odourless as possible.
