15:29
Well I found a few more tactics, and a new way to despawn. Apparently the game can only handle about 4 enemies on screen at a time. Get a few enemies to chase after you and it's possible to stop enemies from spawning as you advance. This really helps in Act 3 by keeping just in front of the flipping clowns since it has another unintended side effect: the flame spitting devil clowns can't always shoot fire if there are too many enemies on screen. Even though I still have to take a shot to get by them, it's from contact damage, not fire damage (so about 1/2 bar compared to 3 bars, nice trade). Too bad it only works for the first fire attack, but that's enough time to get by.
I also figured out that in the right situations smoke bombs are really overpowered. Any enemy that gets caught in the blast is frozen in place and all collision boxes are disabled for 5 seconds. Any hurtboxes that aren't projectiles still stay active, so you'll have to avoid those. Most projectiles are immediately despawned, but I believe ONLY if they're also caught in the blast.
Right now the biggest areas to abuse smoke bombs are 3-1, 3-4, and 5-1. There are other areas I could use them, but my current route doesn't leave too many extras to use.