My own personal setup is a Vac and or Blower plus half face Respirator for Safety--This is ESSENTIAL!--and with a big airgun and a few custom fabbed depth gauges I can swap teeth on my 76HP tow behind in 10 minutes or less. Even less time on the RG50 or the little 25HP "Promark" based custom. I buy CAMEL brand green wheels from MSG mainly (machine tool supply), 8" Dia., 36 GRIT---Go rough, we aren't sharpening tools for the Southbend or the Bridgeport here. First you Dress your Grey wheel (with a Diamond single point) to a keen corner in order to grind away (Back Grind) the steel supporting the carbide enough so that when you grind the Carbide itself, you won't be grinding steel as well. If you execute this setup correctly, you can quickly rotate "New"or "Newer" to the high pockets on the powerful machine(s), and the re-sharps to the smaller machines all while maintaining the hierarchy of "Healthiest" teeth in the most demanding locations, and the most re-sharpened (half or more even) relegated to the lowest pockets on the smallest machine. I've also found that Proteeth by Rayco outcut anything else on the Big Dog, but not by enough to justify the price to me.
Sharp teeth really are important, running dull isn't just slow, it will beat up your bearings, shafts, turntable etc. Running dull is False economy. Also, if you can't find the 36 grit, go for the 46 grit, Either one will cut SO Much faster than the 180 or 240 grit or whatever wheel they might try to sell you--that's toolroom stuff, we don't need super fine surface finish. Diamond wheels are fine as well, but the same rules apply--Grind carbide ONLY-not the steel (or you'll clog/rapid wear it) and chase down the Coarsest grit you can. Still, the cost of diamond doesn't pay off in speed or lifespan over the "Grey wheel/Green wheel" Setup. That's my .02, but I've been at it for around 20 years and have converted a few people along the way. I've also Brazed on replacement carbides where the steel was healthy enough to support it--Rayco Proteeth mainly.
Depending on your local flavor of dirt, it may pay to hardface the leading edge of your pockets--I've done that as well, and weighed them to avoid a balance problem but found that it really wasn't needed (weighing that is).
We've got a lot of Scrub Pine here in Jersey--on the north edge of the Pine Barrens(!) and even the biggest machine with dull teeth will look like you're trying to cut a Truck tire with a Ball Pein Hammer. Also, if you can't find the coarse wheels listed, call around and ask, Camel is from Israel (one's I've gotten) and they're worth the special order.
I've tried the hand grinder on the machine deal and it just isn't as quick or easy as a proper shop work station setup, and most days I only change out the highest teeth-the next row down sometimes every 5th time and so forth. Beyond that, I keep the bearings greased, have spares on the shelf and on the small machine I've found the 15 dollar chinese bearings last just as long as the 100 dollar Timkens. Big machine, different story, but do shop around, i recently bought 4 double row 2 15/16" pillow block bearings for $186/ea, Link-Belt branded Timken, but I also was quoted over $500/ea for the same part from the dealer(!)
We've got really sandy dirt here, so we try not to drag it into the cut as much as can be avoided if it's a big stump and we have to use the small portable, but eventually it's pretty much unavoidable...And the one last thing is that I always use Loctite bearing mount when setting new bearings. I've never had shaft wear when 620 Stud n bearing mount is applied, BUT--the trick is to be sure you have a fast clean shot to the correct landing spot on the shaft-it sets quick and you pretty much need some real heat to get them loose once they set. Yup, I'm "AR", but I hope I helped someone, Regards, Mike