I am currently learning Any% (No up+A) runs for Metroid and am having trouble with Kraid. I have watched many videos of runs and have tried to replicate the strategies used, but I cannot get any of them to work consistently. I was just wondering if people had any tips for this boss, or if there is a subtle trick that I'm not seeing in the videos. Thanks in advance.

select mashing is the key.

what exactly does select mashing do?

Hold "B" and tap "Select" makes you shoot more bullets :)

for me. most important part is freezing his low projectiles in a good spot where you can sort of use them as a backboard. after that, you need to hug him (to get more shots in) and as bb said, hold b and tap select and the directional. The directional tapping will get you close, but it also makes you shoot faster. AFAIK, once you hold B, hitting any button is the equivalent of hitting b again so it increases mash speed