This chapter was made at least 100x easier due to Haystacks, who recently discovered that turret gunners never count as kills (in case you're suspicious, the 4 kills in the chapter are from the cutscene where Mike gets blown up, NOT from the 4 gunners I kill). They are, by far, the worst part of doing this chapter, both for no damage and for minimum kills. Without them, though, it's a breeze with a decent strategy.
There's nothing super radical about the strategy I use for the 3 gunner section. Note that the Broken Butterfly is great for the rocket launcher soldier, since 2 shots will disarm him. If he still has his rocket when you head to the other switch, he will always shoot his rocket, and he's almost guaranteed to take himself or someone else out. For the key card area we can use the exit/reenter trick to fool the game into not counting the key card soldier kill (thanks again, Haystacks!). I accidentally shot the key card soldier in the legs, making him fall down, so this took a bit longer than it should have.
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