What you can to do for this achievement is set up a 4 player game with one controller. This is straight forward from the set up menu.
The Grab Bag round will be round 2 or 4 if you select a 5 round game. What you want to do is select the wrong answer on purpose with the three players you don't want to get the achievement. This will leave your lead profile to select all eight correct answers in the grid.
The questions are random so pick a category you know well and Google the answers if you get stuck. Happy hunting.