I sometimes use a three-note twiddle on the same side, with the third above, though I'm guessing you cover this.

Another ornament I sometimes use is to intersperse a few drone notes between melody notes or broken chords. Sounds harder than it is.

You can also add short chromatic runs. But seems the accidental I want is never where I expect it to be, unless I work it out beforehand.

Which brings to mind: Do have advice on how to recover when your fingers end up on the wrong row or column, and you sound like you're having a sudden psychotic episode?

Also, do you ever add portamento by wiggling the bellows?