Measure the height of the tin from the bottom of the lid. You want to make sure the lid will still fit after you are finished decorating, after all!
Indicate the lid position using a fine-point permanent marker (unless your tin has an existing guide).
I found some great tins on clearance at a local craft store, which is what gave me the idea. You can also re-use Twinings tins or other airtight canisters.
Spread glue** evenly over the surface to be covered. DO NOT spread glue over the lid-line. If you are using an industrial glue, you will need to work quickly and in a ventilated space (you twisted little glue-sniffer).
**Choose a glue to match your materials. For metal tins, use an industrial glue like E6000 or Liquid Nails. If you have a foil-lined paper canister (like a cocoa container), you can use a tacky white glue or my new personal fave, YES! paste.
VARNISH it baby! You want to protect your work, don't ya?
There are a plethora of varnishes from which to choose, so pick your favorite whether it be gloss, satin or matte.
Wipe off any varnish that creeps up over the lid-line. Ensure that the varnish is not just dry, but allow plenty of time for it to cure before using.