“Speed running paint”? You mean opening the image and dragging a text box over the existing text, changing the font to comic sans, and typing the text?
There are complicated workflows in Paint, this is not one of them.
Why have you failed though? Is the point to try to deceive people to think that XKCD actually published something else? Why not modify the xkcd one without hinding the fact that you modified it?
There are complicated workflows in Paint, this is not one of them.