First thing comes to mind is bad inside grease seal or leaking wheel cylinder.
The grease or brake fluid contaminats the shoes, makes them grab and wear down fast.
You can look at the inside wheel or the backing plate for stains.
Jacking it up should be just inside the wheel on the axle tube or spring perch. I stay close to the tire so I have room for a jack stand.
If you can't fit under, drive it up on blocks of wood first for clearance.
Be sure the 6 or 8 ton bottle jack is on a level solid base.
Good luck with it.