Is there any other method of braking apart a rear cog cluster than using two chain whips in the opposite direction?

....this 78 schwinn is killing me

Heat......as in plumbers' torch, assuming the cluster is off the hub...

Try putting some long pipes on each whip or one whip to increase your leverage.

PS: If there are spacers in the freewheel, save them. They come in real handy for spacing the rear cog for chain alignment.

Get a small metal pan. Put 1/2 bottle of inexpensive whiskey in the pan - set aside, but you will need this later so keep it handy. Get two sections of pipe and attach them to the whips with Duct tape (as per don d's post) and lay them next to the pan. Set the bike up for fixing (ie-place in stand). Drink whiskey from pan FAST. Become instantly stronger and at the same, the world's best bike mechanic. Problem solved.

so I may as well not worry about breaking up the cluster and put a new cog on when I put on new wheels

Why are you trying to break up the cluster? Is the freewheel already removed? You're not going to be able to break up the cluster if it's off the bike unless you have a freewheel vise. Did someone tell you you could use a cog off the cluster as your fix cog? What are you trying to do?

your ideas intrigue me, and i wish to subscribe to your newsletter...

it is all in the beverage...
As our American Icon, Homer J Simpson once said, "To alcohol! The cause of... and solution to all of life's problems!" Also applicable: "Trying is the first step towards failure." Heh heh heh...

it is a freewheel hub, there is no cassette, so I was going to break the cluster apart and use one of the existing cogs for the fix