Hey, I'm starting with the punch out speedrun for the first time.

I don't know if this works for others, but at least for me, in the 'Punch-Out!! (USA, Japan) (En)' ROM (I'm not sure if ROMs change in this game), I wait until exactly 36 seconds for Glass Joe, then instantly buffer 2 left uppercuts. When he starts backing up at 40 seconds, I buffer 2 left mid punches, and finally, at 41 seconds, I time the right punch to knock him out.

It works for me every time. I've tried it about 30 times, and almost every time I get 42 seconds. (Some other times I just fail the last right punch timing)

So tell me what you think.

This sounds like you still have to time the last punch manually in order to beat him. Also, when saying "uppercuts" I think you mean jabs because it's only possible to get one star before he backs up at 0:40. You do seem to be describing a buffer that already exists.

When the clock hits 0:38, buffer two face punches. If Joe beeps twice, throw two left gut punches and one right gut punch. If he beeps 4 times, buffer four left gut punches.

Or, staring from 0:00, you can buffer 22 face punches followed by the strat above.

Yes, I meant jabs sorry.

But I do it like in 36 seconds those two face punches, then I always do two left gut punches and one right gut punch every time and at least it works for me, I don't know