It'll be easy once you get the first Lucemon, easily finding Angemon in Fighter personality to de-Digivolve one. I kept grinding in the farm until it was enough, and I didn't want to go for extreme training because I am such a emotional person lol.
On my team now: Rosemon BM, OmniShoutmon, Omnimon Zwart, Lucemon, Ouryumon, Dianamon, Beelzemon, AeroVeedramon and Sistermon Ciel. I don't have enough Memories left so, training AeroVee to be UlforceVeedramon and Sistermon Ciel to either Sistermon Ciel (Awakened) or Lilithmon. All of them have their ABI over 100 now. I find it easier to force encounter and have the Battle graphic thing turned to 'Short' beside a booth to the DigiLab. I also Load Digimon to the ones I need levelling up after they get harsh training.
For my Switch version I am trying to gain an all-no-anime-characters'-monsters-team.
I spent like 2/3 of my time training lul. I guess I'll only be able to play Hacker's Memory part after I am done with Sword and Shield.