Thanks again and I think I've put my finger on my Proton issue.
#1, the battery did need to be replaced. The CB1 is supposed to "see" 9V. I know from a past experience that it will still function when the battery is down as low as 6V (perhaps lower, but I once reached and then measured 6V from the battery so that's my "tested" lower voltage limit) but the tone/output is affected. Replacing my battery made an audible difference (it also let me ease back at least an "hour" on the Proton's gain pot). I also very slightly raised my PUP heights which helped, too. I'm definitely not now having issues triggering the effect.
My issue - to the extent I actually have one, maybe the problem is my own in that I just haven't practiced enough with the effect to adapt to how best to pick with it - is not with the triggering, it's with the decay. This is a guitar I've never had any sustain issues with before whatsoever but with the Proton the guitar's notes - not the effect's decay frequency level but the overall decay of the guitar's own output - are not sustaining as long as would be ideal for this specific effect. At least that's what I'm hearing/feeling.
With my Line 6 M13's Tron Up model, as noted previously, I'm preceding the effect with a compressor. I set it up this way primarily to limit my upper volume threshold to avoid sharp and unwanted high transient peaks. But now that I've analyzed it further and A-B'd it with my Proton, it's clear to me that the comp is also serving as a sustainer - it's keepin my guitar's signal active longer than it would be without the comp (where it fades out faster) and this is a big help with using the Tron Up model.
Not sure what my next step will be but at least I feel now that I'm better understanding what I'm working with in this regard. (This experience has also benefited me in that, as a result of it, I've gone back and revisited several other aspects of my rig that I hadn't changed in a long while, making some [I hope!] further positive adjustments.)
One followup question I do have is did Jerry precede his MuTron with any effect (turned on, obviously) that would have served as a sort of "sustainer?"
P.S. to waldo: Just want to confirm before ordering - the regular Jerry version of your buffer, i.e., the not-unity-gain version, am I correct that its output is slightly less than unity?
"For me, I think the only danger is being too much in love with guitar playing. The music is the most important thing, and the guitar is only the instrument." Jerry Garcia