I just do the OLCI as soon as it opens. The app asks you if you like to get on the list for C+ upgrades and whether you'll accept a middle seat or not.
I think the main advantage of this hack is that you can select seats (including exit row and seats in the first few rows of main cabin) at the time of booking.
If you happen to get an upgrade to C+ on the DoD, great. If not, you're paying the same price as DL Basic Economy but getting complimentary ASR by going the AF/KL codeshare route.
Neither the outbound, nor the return worked with the app request. I got an error each time - "Oops we're sorry.... process complimentary upgrades failed". I also couldn't see the upgrade/standby list on either flight.
The big issue here is that these were relatively empty flights, half dozen or more empty C+ seats each way... so it shouldn't be, "if you happen to get it great". It should be, "if it's available you should absolutely get it" - and you shouldn't be made to have to show the website to multitudes of people". you agree?