Not sure about frozen because I don't wait, but I've tried it with freshly killed coyotes and you can still tear the outside ear skin if you are not careful. If you are just tanning for display then I'd take a few minutes with the spoon handle or maybe a round bladed putty knife (no corners or sharp edges) to work between the cartilage and the outside ear fur to the edges. Some trappers I've seen can work the ear apart with just their fingers and some borax, but I don't know if I've got strong enough fingers for that.
If for some reason you come across a torn up roadkilled yote or maybe shoot a big ole hole in one you can still use it to try the screwdriver method out as "practice".
