The grinders get me a lot in my any% speedrun attempts. On the PC version, I tick the V-sync option to lock the games frame rate down to 60fps and I can usually get passed them pretty quickly as soon as grinder starts going up as soon as it goes down. I did a run a few days ago and got 20:16 in-game time and I managed to get passed both grinders without a quickload!
Edit: You might want to have a look at my any% boardroom speedrun that completes the level in 0:59 in realtime.
https://www.youtube.com/watch?v=1b9yWRy4EPo