Mac,
I don't understand why you would think that some form of trickery is required to load the 458 up to spec.
I worked up loads for mine using the same Australian powders that are used for reloading my 308 and 30-06!

The technique is the same and just as simple as reloading a common easy to load cartridge like the 308 or 30-06!
The only extra work is to crimp the bullet which I do anyway with all big recoiling rifles! (providing there is a cannelure of course)
Trim case, seat primer, dump powder, seat and crimp bullet!
Hell , it's actually a lot easier than some NE reloading for doubles!

Talking velocities, as stated earlier, the 500 soft ran at 2120, the 500 solid at 2080 from the 22 1/2" barrel.
I also had some 300 grain welded core bullets running at 2700!
Incidently, apparantly in 1961, Rifleman magazine published figures of 2087 fps for a factory 458 load in a 25 inch pressure barrel tested at HP White Laboritory.

With Graeme Wrights velocity tests showing that NE cartridges often run up to 100 fps less than their claimed speed, that 2087 fps shows that Winchester was a lot more honest with claimed velocity than some of the others!