I dove in head first haha. I use a pop-up dictionary (yomichan? yomitan? whatever it’s called now) but for very old works often my dictionaries won’t have it and I just google it. Sometimes googling weird grammar + 古語 works too. Getting familiar with old kana spellings is something I just did over time by the above method, but @pm215 made a nice cheatsheet of old spellings here for last year’s challenge which you may find helpful!
Edit: For post-war none of that is really necessary, but the farther back I go in history the more it is 
Also worth noting some works have ‘modernized’ entries with the reformed kana spellings and (I think) modern kanji usage.
