I have tried several things.  Scissors work best for thin slide soles. but what do you use for the traction soles and heels.  I have tried scissors, tin-snips, and box cutters.  All of them kinda work and none of them really produce good results.  What do you use?

I think that what most people think of when you say "box cutter" is nowhere near sturdy enough. You need a woodworking utility knife, something like these:
http://www.uline.com/Grp_24/Utility-Knives-and-Cutters
http://www.uline.com/BL_1170/Uline-Comfort-Grip-Knives

I have a collection of "box cutters", need one? They work good!

I trim and cut my soles in half 60/40. my slide soles, I have #10 up front and #8 which equal #9

And I trim my round heel.....

I'll pay a shoe smith to have mine done to make sure it's done right.

I've never had a pair of Dexters last long enough to worry about replacing a heel.  I've got a stockpile of extra heels.

Band saw for heels. Scissors for slide pads.