I don’t know what’s wrong with not opening the air button fully, but at all events, assuming that you’re not playing the basses much at this stage, your aim is to keep your bellows from opening very far at all - especially if you’re playing mainly on the row, C#/D style.
Watch good Irish-style players and you’ll soon see how little bellows travel is involved. This is important for precise control over the bellows - try playing a fast in-and-out passage with the bellows wide open and you’ll see what I mean.
To maintain this small amount of travel, you need to use the air button constantly, and you need to do it while you are playing notes.
For example, on a C#D box, playing a typical Em tune, if you don’t use the air button your bellows will gradually extend farther and farther open. Don’t allow this to happen - as soon as you get a note on the push, say a D or an A, open the air button and as you play that note bring the bellows in farther than they would go naturally.
You might also find yourself doing the same thing in reverse in the same tune, opening the air button to open the bellows a wee bit to get yourself into position for a passage involving several push notes. Nothing wrong.
If you’re playing many D tunes on C#D box, you’ll be using the air button frequently on pull notes. It’s the nature of the beast.
Opening the air button fully while you do this, I think, will tend to take all the guts out of your note. Even if you open it slightly, you’ll need to compensate with extra bellows speed to stop the volume from dropping too much.
This is a very different style of playing than say, French players of G/C boxes, who play across the rows to to avoid pushing and pulling and open and close the bellows quite wide over long phrases. Generally we don’t have that possibility on half-step boxes.
Playing the basses intensively will increase the amount of bellows travel (ever watched Tony MacMahon playing?) and might involve you in opening the air button fully I suppose. But for right-hand playing, I think that using it little and often is the way to go. Don’t know if that constitutes “riding”, but that’s what I do anyway, and I’ve read advice from very experienced players to the same effect.
Anyway, I wouldn’t worry about it too much - it soon becomes second nature.
Cheers
Steve