I have both versions of that park tool but a 2x4 works better for overall alignment. (different hook sizes) I only use the two park tools (at the same time) when I'm trying to bend a stay mid-stay without bending the stay at the bb a the same time. If you use the park tool you need something to leverage against. Just having 1 park tool only works if you have an immovable anchor for the frame. I've broken 4 bench vises in half trying to remove bb cups, etc, and my bench (with the vise) isn't rock solid.
With the 2x4 you use the floor and gently step on it. Worse case you have to lift the 2x4 and have the wife stand on the frame to hold it down.