Bart doubled back to take Tommy's wrist again and when Tommy began to slow, to stop keeping up, Bart tapped into the Speed Force himself.
It seemed to fill the air like a snowy wind, swirling around and sinking into Bart and, through Bart's physical connection, into Tommy. It seemed that the Speed Force couldn't tell the difference between the two, which was partially Bart's doing. He knew that if he had a physical connection with someone, the aura of the Speed Force that surrounded him when he used it and was in it would also protect anyone he was in physical contact with.
With this extra burst of speed and with Bart dragging him along, they didn't go much further before the world that was around them, the world that Tommy was trying to look at to keep from running straight into anything, was gone and replaced by streaking red and yellow blurs. There was nothing but the afterburn effects of the Speed Force around them, Tommy, and Bart from whom little sparks were bursting off of, tiny lightning bolts streaming from the corners of his eyes.
"This is the Speed Force. It's where me and the Flashes get our power from. This is where we go when we die. It's like... did you ever see Star Wars? It's like that, if Speedsters were Jedi/Sith." And Bart knew some Sith who could use the Speed Force just as easily as he or his Grampa could.