In order to Unscrew the small cog you have to Immobilize the rest of the cluster in the direction that it freewheels ..

(perhaps the trick of zip tying the biggest cog to the spokes may be considered)

Why not just use 2 chain-whips? If you dont have any the LBS will .. I have those tools ..

I wouldn't bother tearing down a Multispeed freewheel just replace It .. cogs for them havent made as separate parts for a very long time.

Im Old , I just do mechanics, not Videos ..