Commercially I sharpen nowhere near the volume of some of the BF pros, but have done plenty. You are lucky if the knife has simply been used to the point of extreme dullness with maybe a ding or chip. if it has been poorly sharpened repeatedly are the worst because you have to correct the geometry first.
In many cases (kitchen knives) the bolster has to be ground back. The blade might need to be straightened (I have a small vise with three adjustable contact points just for doing this). The tip will need to be reformed. You need a very coarse stone or moderately coarse belt and as few progressions as one can get away with. Aside from a stropping belt, I use no abrasives higher than a 220 as it isn't good use of time and grind quality for the work that gets done.
As to the burned edge discussion it is entirely preventable. Worn abrasives are the #1 culprit. Running too slow can cause more problems than it solves and reduces belt life, save it for the diamond coated abrasives. Doing too much work with belts much above 220, esp as you get closer to 800, 1000+ grit - these heat the edge more rapidly than a 120 grit belt and need a close eye on contact time etc, also belt condition becomes increasingly important. A worn 1000 grit belt will cook your edge in a heartbeat.
. Folks who sharpen professionally report lots of knives not well maintained. It would be interesting to build a report comparing their experiences with that of Blade Show's "birds of a feather."
