In my view all that kind of stuff is a lot less essential to good box playing than to piping. I'd work on learning to play tunes simply with a good swing - mastering the bellows and the air button - before I worried too much about ornamentation. The bellows are your bow!
That's exactly how I feel about concertina, except that, since I don't play fiddle, I wouldn't have mentioned the bow. Your best friend when it comes to good rhythm, articulation and expression is bellows control.
I'd add one other thing. Get very good at playing triplets before you worry about other ornaments. I don't know if this would be good advice for accordeon.