I just buy new plugs, but I have some friends who swear by cleaning their used plugs. Is it worth the time and effort to clean used plugs, I don’t think so.

It saves you a few dollars, that's about it. Not worth it in my opinion.

If only carbon fouled, it's an easy job with a fine grit blaster.
But plugs with mileage/erosion, not really worth it.
Unless maybe plugs are very high $$$, or hard to come by.

i clean them and stick them back in or set them back for later all the time. it's easy to inspect plugs for wear or erosion and those i don't keep. it's a choice. do what makes you happy.

back in the days of leaded fuel the 340's had a tendency to misfire / cr-p out under full throttle at higher RPM levels with more than about 500 - 1k miles on the plugs. A new set always corrected the issue as well as using one of the abrasive / air blasters like the
one pictured, they come in handy once in a while

Unless the plugs are carboned up, I seen no benefit to cleaning plugs with today's unleaded fuel. In the old days with leaded gas, grit blasting would remove the lead residue on the porcelain and dislodge "clinkers".

I always wondered if all the abrasive can be removed from the plug body, or does some of it end up in the cylinder...

The plugs on my 451 Dart with underchassis headers are sufficiently a PITA to remove that I always replace them with new ones!

In the early 2000s Chrysler used as OEM spark plugs Champion “Double Platinum” that have two tiny alloy discs per spark plug.

On the original OEM plugs and a replacement set, one or more these tiny alloy discs broke loose on my Mom’s 2005 3.3 V6 causing misfires.
These Champions were supposed to last +75,000 miles.

It is really hard to spot the missing disc because even when gone there is a circular weld mark.

A KAL 2969 computerized spark plug analyzer could not reliably spot the misfiring plugs, perhaps because of the “wasted spark” ignition system.

Sandblasting a used spark plug in my opinion could easily knock them off.

Maybe blast with baking soda or dry ice?

I switched to NGK Iridium tip spark plugs and the engine ran noticeably better all around, especially climbing steep Interstate grades.
No problems since.

The units like the one I pictured above have 2 settings, 1 for the abrasive, and one for straight air. I have usually found a piece or two of the abrasive up inside between the ceramic & metal. A blast with a regular air nozzle, dental pick or similar device quickly dislodges them. If you're really concerned a blast with brake clean or alcohol will get any remaining dust.