Are there any guides on the marvin radio scene cancels and the c4 rocket whatever cancel thing? Like I don't know their official names. I've been trying to pull it off from watching the top runners but it seems to be like a perfect timing thing?
For the C4 Rocket strat, you only need to stand right in front of the C4 and shoot when there is only 1-2 seconds remaining so that when you shoot the rocket, the animation that Leon/Claire does gives I-frames and isn't thrown back by the C4 blast. I usually aim at the floor while standing as close to the C4 as possible. I'd recommend making a save (at the bottom of the stairs) and practicing that.
Now as far as the Marvin cutscenes are concerned. The library skip you basically shoot towards the middle of the corner square on the ceiling, all while walking into the cutscene trigger. It does take some practice and timing to get down but you can again use the save I recommended to practice. Now for the 2nd Marvin cutscene skip, just aim at the floor as soon as you can take control of Leon/Claire and walk into the call trigger and it should skip it. Hope this helps!
for the first rocket, you shoot the rocket at the ceiling just after you walk past the first pillar and you keep walking forward. the second radio call, you shoot at the ground and you wait for the stagger animation to finish then you can start moving.
Seconding what Levi said, He taught me the skips back in 2019 :) adding my character-specific knowledge: regarding the second Marvin call outside in the rain, Leon may fire and instantly move to the door, Claire it is advised to fire the rocket then wait 1-2 secs for the dust to clear before moving, premature movement may cause the call to click in late which is hella annoying as you feel like you get the skip then it happens last second and screws you. Best of luck to you on your runs!