New speedrunner here looking to give this game a shot since I love this game as a child and watching curtissimo.

I've been trying to figure out how to do the Fire Cancel, tried watching videos but there isnt any information on how to do this properly, I just want to practice it but I have no idea how to even get it done

Very delayed but just to give this thread a response:

You want to be in the air, use fire then at the end input A for a float, then quickly hit B to puff, then after a tiny delay hit B again to fire. The timing for the first two fires is later(the fire goes further) than the third and beyond so I often would just spam A and float on the first two to not lose height before getting to the easier to time part where it's all the same. After the fire I kinda roll my thumb from A to B, the puff can be quite quick after the float. Maybe rolling isnt the term for it(my thumb isnt moving) but just quickly transferring from pressing the joint of my thumb down to the tip. Then I manually time the B press for the next fire. I think some people mash but for me it felt like learning the timing was the way to be most consistent. At first you'll probably lose a bit of height but with practice you slowly get better at maintaining your height.

Quick segment with input display for reference

Additional notes from SK in a previous thread: https://www.speedrun.com/k64/forums/irzvs