Easiest would be to use the 3" test T. Your plumbing supply house will have a test plug that you can screw into it and the balloon hangs down into the pipe. When you want to take it out, you can let the air out, then I'd still slowly unscrew it. I did that and even after I pulled it completely out i didn't get any water on me. I can't find the one I have online to reference, but it was about $30 with tax.
edit: The link above is what i was referencing.
edit: The link above is what i was referencing.