BTC stretching , how is it done properly?

Hey TP, I started up PE again and I was doing manual stretches for awhile and wanted to get into more advanced forms. I tried BTC stretching last night but I couldn’t seem to pull it off, my balls got in the way when I tried to pull the penis down between my legs.

Can anyone explain the correct way of doing this?

Pull your dick to one side of your sack and move your sack to the opposite side.

This photo pretty much explains it.

BTC Hanging Photo