I have 4000 puzzles to filter into Easy for the find-the-word mode. ESL-type word lists don't really help as we need to match the word form exactly.
I think the manual approach is least hours of effort (given that time has to be spent researching and programming the alternatives). I will write a command line tool which shows me one word at a time and I will hit 1 for easy, 2 for maybe, and 3 for hard. Doing one word every two seconds will take 8000 seconds or two hours. Proper programming the solution would take much longer, and would yield lower quality.
The way I play Puzzle Mode, I don't particularly care that I don't know the word. It is enough of a challenge finding good clues, and there is the fun of using the rules of spelling to deduce what the word must be from the clues found and the letter pool. But I imagine I am a good player, and my average is only 343 (max 1000) so the game is too hard. It was even harder before I let 5-letter words unlock clues
I find I play puzzle mode mostly now. It is exactly the right length to play while waiting for the metro or the kettle.