The way I do it is I just run and dodge. You'll come across scrolls in the level as you try and find the exit. Sure you'll miss some, and yes enemies drop them, but you really only need to think about survival when doing a speedrun like this, not your damage. After a while, the ones you come across naturally will equate to good damage anyway. Not to mention you also get one (or two) behind every timed door. Prioritize leveling up tactics/purple because they'll be way more helpful when you DO get surrounded, or when you DO have to go through enemies.
You're not running it this way to beat the game (though when I finally beat it, it was what I was doing haha), you're running it to get cells and blueprints, and because it's really fun to play this way :) So don't worry about missing too much. Over time, you'll start getting better stuff as you do it, and eventually you'll be naturally fast, and you'll be finding better stuff. I prioritized upgrading the quality of my drops (you unlock that once you beat the second boss I believe), tactic items, the potion, and getting the random starting weapons.
This ended up killing the increasing feeling of repetitiveness because the challenge was no longer killing enemies, it was running past them and seeing how fast and fluid I could go through levels.
It might not be for everyone, but I love playing this way.
