1. Play as Jill.
2. Play on very easy difficulty.
3. Run like hell, you can avoid most of the enemies by simply running right past them and hitting the next door.
4. Avoid the plant 42 fight head-on by killing it with V-Jolt.
--Combine 1 (water from the sink) and UMB No.3 to make NP-004.
--Combine NP-004 and Yellow-6 to make UMB No.10.
--Combine 1 and Yellow-6 to make UMB No.7.
--Combine UMB No.10 and UMB No.7 to make VP-017.
--Combine VP-017 and UMB No.3 to make V-JOLT.
--Take the V-JOLT back down to the Aqua Ring and use it on the roots inside the guard room.
5. Save your big ammo and guns for the boss fights.
6. Do not save Barry or Chris to avoid the 2nd boss fight with Tyrant at the helipad.
7. Save as much as possible, especially after boss fights.
I followed the path in the speed run below.