Correcting Long Sits

I received this advice from a friend on how to correct problems with the long sit... The only thing I wonder about is if I should use our "oops" command, which he already understands.

Here’s what our obedience trainer suggests: Put the dog in a sit, with the collar (I use a martingale) loop at the top of the dog’s neck. Stand close in front and notice the first signs of starting to go down. At the first sign, return to the dog, say nothing, gently and quietly straighten the dog up by the collar without saying anything, and return to standing in front of the dog. The point is to neither reward or punish but just reposition—no words, no pats, no nothing. To get longer sits, you can walk back and treat periodically for good sits.