wiedemann:
In considering this issue, we decided to take a ride and make mental note of how and when we engage our turn signal switch.
As an aside, we find that taking a nice ride often gives us the opportunity to sort through various issues or problems in our (relatively happy and stable) life. We find that a ride often resolves mental, spiritual, marital, or whatever sorts of problems; and can be quite theraputic. Hell, a ride (and a bit of laxative) even helps us with occasional constipation. We rather expect that many of our fellow riders find a pleasant ride to be similarly beneficial (excepting possibly the constipation).
Anyway, this morning before a ride we tested the procedure of engaging the clutch and turn signals simulteneously, and (like you) found it to be quite difficult. Then we took a nice jaunt and we found that we never had occasion to engage both the clutch lever and turn signals simultaneously during normal riding. We were ether between upshifts or downshifts when we engaged to signal or to cancel.
Based on this (admittedly limited) test, we must conclude therefore that your problem is a simple matter of riding style. We would never presume to tell another rider how to ride, but you may find that a slight adjustment in the timing of your signaling will put things right.
Our $.02.
We trudge on.