Audi key fob resync

Years ago I replaced the key fob battery on a 2004 Audi A4 tdi and resynced the key fob after it stopped working. I dont actually remember what we did but I could swear it involved pressing the unlock button multiple times while sitting in the car with the doors locked. Now Im trying to do it again years later and all the instructions for it tell you to turn the key in the ignition with the unlock button held down for 2 seconds, like this tutorial:

https://www.ebay.com/gds/How-to-Program-an-Audi-A4-Key-/10000000178627435/g.html

Im 90% sure thats not how we did it though, it was something to do with being in the car with the doors locked, I dont have a second key to use either so cant go down that route.

​​​​​​​Can anyone think of a different way of doing it with only one key? Thanks.