Levering with a screw driver can cause damage but an open ended spanner of the right size acts as the perfect lever with the tip of the lower jaw under the seal edge and the curved part of the jaw as the fulcrum on top of the inner bearing.
[Emphasis Added]
I had the rear off just the other day to repair a flat and used Mr. Korn's greasing tool to freshen up the bearings at that time. Â For situations like that, I think its great. Â Anyway, I hope you can bear with me here, because I'm not 100% sure I understand the technique you described above completely enough. Â
If I understand you correctly, you "lever" the seal out by moving in a crisscrossing manner along the outer circumference of the seal while extracting it. Â I had not tried to remove the seal, but from what I remember of it, wouldn't levering the inner circumference work too, maybe even more efficiently? Â There seems to be more give in the seal based on its design, as that would make for ease at fitting the spanner's lower jaw tip underneath its edge, rather than along the stiffer outer edge.
I am planning on ordering new seals anyway, but it would be nice to know how to do the operation just the same...
All the best.