The good news is that this works just as well when you’re out camping as it would in a serious SHTF situation.
First off, locate the roughest piece of concrete, asphalt, or a relatively flat rock nearby. The less debris and dirt on the surface the better.
Next, rub the top of the can against the surface, sanding down can’s raised seal. Keep checking every few seconds to determine when you’ve got it sufficiently worn down.
Preferably, you’ll notice and stop sanding before the contents begin leaking out. When you see moisture leaking out, you’re definitely done with STEP 1.