wailing away on a stubborn S.O.B. with a 5lb hammer. Plus, the sacrificial 2X4 prevents any damage.
A few years ago I had this problem and wondered how the tire stores here in the Midwest (where road salt really speeds up dissimilar metals corrosion) handle this - they use a really large & heavy (felt like at least 15 lbs) plastic coated sledge hammer and they swing it at the rim directly - no 2x4 in between.

I've found through personal experience that banging on the tire does no good - the tire absorbs too much of the impact. I've also found that a 5 lb sledge isn't enough - you need more mass - I use a 12-15 lb sledge and I hit the rim directly. I've found putting a 2x4 in between absorbs too much energy.

If you use enough mass, you don't need as much velocity (and it's hard to swing a heavy sledge underneath the car parallel to the ground about 6" off the ground anyway, so you can't generate much velocity). If the rim breaks free (and it always has for me) it doesn't damage the rim at all since none of the energy is absorbed by the rim.