Wet conditions through much of the corn and soybean belt have stymied harvest and will probably contribute to a flush of calls about combines that are plugged. Callers want to know a quick way to unplug feeder houses, feed accelerators, threshing cylinders/rotors, discharge beaters or straw choppers. The bad news is that if it's bad enough that they have to call their dealership for advice, it's probably not going to be an easy, quick process.
The first thing to do when a plug develops is to resist the temptation to rev the engine to full throttle and slam that sucker into gear. There's a remote chance that that technique might clear the plug, but more than likely it will just wedge things tighter. If a machine starts slipping belts, and warning buzzers are going off--surrender. Cool down the engine, shut it off, and start taking off shields to see where and how bad the plug is.
Loosen and remove the drive belt to the plugged component, then manually (wearing leather gloves) pull out as much of the plug as possible. Then get the biggest, longest, stoutest pry bar you can and use it to try and rock the drive pulley/sheave back and forth enough so you can pull out a few more handfuls of the plug. If you can't get a pry bar into the drive pulley, then get inside the machine and stick the pry bar between the bars or lobes of the component to try and move it. If you happened to plan ahead and installed an unplugging kit on that particular component ahead of the season, those kits provide notches or holes on the outside of the machine specifically designed to let you use a mammoth pry bar to work loose the plug.
If a pry bar won't budge the plug, then it's time to remove grates, access doors, side shields and in some cases major components to take pressure off the plug so that it can be manually dug out. I've heard of guys using razor knives, hedge trimmers, and even chain saws to cut through plugs so they could be manually removed.
Once a plug has been cleared, be sure to examine the drive belt/drive system for damage. Any belt that has slipped enough to have frayed edges or charred sections is eventually going to either fail completely, or contribute to enough slippage so that the machine gets plugged again.
The bottom line is to avoid plugs in the first place. It's better to ease off and slow down for a few seconds than to keep pushing it so that you spend the next two hours manually unplugging a wad.