If you have one of these:



you can make a quick and dirty chainwhip with a chunk of old chain.

Wedge chain in the 90 degree end and pull it over the tool, then put the straighter end on your cog, then wrap chain around cog, then make sure you have good leverage, adjust & tweak if not, then give 'er hell.

* this is not recommended by me in any way, just something I used when I had no other tool on hand.