You want them free of oils and other debris so cle...3Step 3: Applying the Magnets With the tins prepped it is time to affix the magnets. 1) Apply equal parts of the JB Weld Steel (black) and Hardener (gray) to your mixing surface. [...4Step 4: Labeling the Tins Now that the epoxy is dry you can label the tins, fill them up and stick them to a metal surface.