That's what I do, I've only been able to beat the first champ (the mullet guy) with an autofire.
The difficulty curve is harsh, the first opponents are very easy and the first champ is very hard, the next ones are even worse.
How many opponents are there ?
Viewing post in The Arm Wrestling Classic (NES) comments
12 normal opponents. 5 bosses. It can take time to master the technique. The first round of opponents are supposed to be easy so you can get used to it, but it gets harder with each division. You can also put in the passwords to practice on each arm wrestler. Worse comes to worst you can put on the super strength password if your fingers aren’t able to go that fast.
Make sure you’re successfully training too, otherwise you won’t level up and it’ll be harder as the game goes on.
I intended this game to be “nes hard” and in the description of the game it’s says it is. I do have to other games. Plummet Challenge Game which is super easy because you die every level, but it’s all about how many points you get before you die.. and Carpet Shark which also starts off easy and gets harder with which level.
Here's a playthrough I uploaded for speedrun.com to show you it's for sure possible, you just might need to change up your technique & realize the bosses are harder than the normal opponents just as long as you train right: https://youtu.be/6DNKeoh9LX4
Note: I purposely uploaded a run where I lost twice, because it would be pretty crummy if the creator had the best speedrun. Also that's not black nail polish on my thumb. I smashed my finger at work 🤣