> just gently dent the edge of the metal lid, enough to break the seal

I think you need to know about the JarKey (https://www.amazon.ca/dp/B00167Z2UO/). Does the job without any risk of damaging glass or even the jar lid itself.

With only one person needed. And denting can usually be done with an old-fashioned can/bottle-opener, to minimize the chance of cracking the glass jar.