For straight radius necks, I think you'll find, Gregg, that there is really little to want over the "I-beam like" radiused bar. Basic technique applies, that is, get the wood straight as you can, then level the metal. You can use a short wood radius block to give some "cast off" if thats your style (its not mine).
For compound radius, you'll need to use a narrow I beam, maybe only 3/4 inch wide, and have it follow the direction of the string, not parallel to the neck. That is, if you imagine the strings going past the nut area, and forming a sort of "vanishing point" of convergence, the leveling must take place along a radial to that vanishing point, or... as the case is... in the direction the strings.
Both of those methods will give you a wonderfully true set of frets. You need to devise a way to support the neck, so it doesn't bend while leveling. Yes.... as machine tool folks know, the machine bends with the weight of the fixture and tooling, and cutting forces... and DONT LEAN ON THE DAMN MACHINE!. Same with necks. They need lots of support. And the I-beam should be stiff. And the sticket paper should be FLAT. And the pressure used should be uniform along the length of the beam, and very light.. Don't try to level quickly. Let the paper do the job.
BTW, if you mask the fretboard, cleanup is LOTS easier. No grunge in the pores.
As always, do the basics first - before leveling you must ALWAYS <--- even on a new neck! ALWAYS make sure the frets are seated, and correct that if needed.
Dan E's FRETWORK is a good book to get a broad knowledge base in a short time, then go over to Frets.com and get specifics, and or , wreck a few necks in the process.
----- This weekend, I shortened some tough stainless steel standoffs to mount the airbox on my Harley. Had to take .200 off each one. I got them withing +/- .003 using nothing more than a drill press, Dremel, cutoff wheels, sanding drum, and sandpaper with cutting oil..... and PATIENCE to let the tools do the work. Took about a half hour per. Same thing applies with fret leveling. Be prepared to go real slow, take lots of time. Speed will come after the.... I dunno... I haven't gotten that far or fast yet.