This is good advice, (everyone's speed is different, so coming out of an individual's slump is of course relative to our ability).
Whenever I feel I'm slumping, I try to shorten my backstroke, and slightly exaggerate my forward stroke with a longer follow through. This conscious effort seems to help me.
Also, for me, slumping has soooo much to do simply with desire to play. I never really was able to practice because I get bored out of my mind quickly and just start banging balls, but even playing against someone, I often don't have any desire to really play the game. Laying off the game for a while helps that a lot for me.
Exactly, you slow down, shorten stroke take it easy get confident stroke, and slowly back up to speed again.