You could go ahead and add your stabilizer now if you'll put it in an old sock or knee-hi and hang it in front of a return so that it dissolves into your pool. That way the stabilizer should be registering by the time you're ready to lower your chlorine levels to normal. You don't want to put it into your skimmer until you're finished with the frequent backwashings, though. Follow label directions to dose it to 20 ppm but put it in the sock instead of broadcasting it like the directions say. It dissolves slowly, so I wouldn't bother to test for it for at least 4-5 days after you've added it to the pool.

Janet