DL overbooks flights, but few of those wind up in oversales. Trying to game this is close to impossible if you are looking 1-2 days out and impossible as far in advance as you are looking.

Even if there is an oversale, there's not even close to a guarantee that you will be the first person to volunteer, that the comp will be $400 or that the onward rebook will be anything acceptable to you.

This really isn't worth 10 seconds of your time.