The chlorine will drop during the day. What's more important is how much it is dropping at night. Just add more chlorine to raise the FC again. Shocking is a process, not a one-time dose. You'll maintain the shock level until all the visible yellow/mustard algae is gone and your overnight chlorine loss is normal (usually < 1 ppm FC but at the higher shock level it might be OK to be a little higher than that) and then to be sure you'll keep it at shock level for another day or two.

As for those other methods of maintenance with higher FC or polyquat, etc., those may not be necessary. Let's see if we can completely get rid of this so you won't have to use other maintenance methods. Those methods just keep any yellow/mustard algae in check and they don't completely get rid of it.