Boy I've done that too. You won't make that mistake again. :-)
The easiest way to do this is to make sure the power is off.
Most new disposers have an Allen wrench socket on the bottom. This will allow you to turn the disposer back and forth while you are pulling on the dish cloth.
If your disposer does not have this Allen socket, then a wooden broom handle or a similar piece of wood can be used from the top to turn the blades.
This might be easier if you had some help. But again make sure the unit can not be turned on the result could be disastrous.
Let me know how you make out.
Glad to help