Do we think that DeoxIT D-100 is enough better then 91% alcohol to warrant trying that?
Yes. Absolutely, positively, yes. Not opinion, but established, proven fact - and not second-hand, but through my own personal use and testing; including several cases of follow-up treatment and use on the very same piece(s) of equipment that had previously been cleaned w/ Alc (often multiple times), as a proper test. Here are 3 reasons why (I don't have time to re-type this right now):
Iso alc is wonderful, and is great for cleaning a whole world of stuff. I use it all the time. If it's what you have on hand, by all means use it. Do however consider picking up some D100 for electrical contacts / connections going forward. The main issue with cleaning oxidized connections w/ alc is that it leaves nothing behind, and does nothing to inhibit the immediate resumption of the oxidation process as soon as you're finished; and especially with low quality contacts / plating, they will oxidize very quickly. Aside from removing oxidation better, D100 also has ingredient(s) designed to do exactly that (inhibit further oxidation), and in my experience it does it pretty well. This makes it far superior to alc for the purpose. It can reduce your ongoing preventive maintenance / reocurring problems. Lastly, it also contains ingredient(s) which provide some lubricity. This can be of value with anything that involves movement / a wiping action (switches and pots come to mind)
I bought a small plastic bottle w/brush, and a second 'top' w/ a syringe-type 'needle' applicator for reaching difficult spots, and w/o waste. I often apply just a 2-3 drops to a swab to apply it efficiently, and for more reach. If you really need to 'flush' something, or reach further, or treat a larger area, aerosol could be in order. Get the form you think will best serve your typical needs. There's bound to be waste w/ aerosol, so I'd only get that if / when I specifically need it (although given my experience now, I may do just that to have it on hand for certain such situations which I'm sure to encounter). I need use it only very sparingly, and if I had kids, I'd likely be leaving much of that small bottle to them.
The fact that the Alc (probably) helped your light temporarily would suggest the issue does involve oxidation, and if so, doing exactly what you did before, but w/ D100 instead will likely keep you from having to revisit that part for quite some time. That has proven to be the case for me. If the Alc helped w/o disassembly, then I'd try using the D100 the same way w/o further disassembly at first. Disassembly might not be required.
As an aside, I even surprised myself again just a few weeks ago. I was threading 2 new, bare Al parts of a flashlight together for the first time, and they did not get along well at all (understatement). The difficulty scared me, and I feared they might actually gall and seize. With equal difficulty, I unthreaded the parts and was afraid I'd damaged the threads, but with only minor magnification, I saw no evidence of that. That first pass improved nothing though. I saw the little bottle of D100 sitting across the room, and although I considered it a long shot, with nothing to lose I tried a couple of drops on a swab and applied just the slightest film to the mating threads. I used so little I could neither see nor feel its residue on either the parts or my finger after touching the threads. Next pass felt remarkably better, but with only maybe 1 more pass, they became probably the nicest, smoothest threads I have on any flashlight parts, and have remained that way so far. I didn't expect that, but clearly is establishes the 'lubricity' I referred to. Being bare, raw Al, and a conducting junction as well, as a bonus I shouldn't need to fear that oxidizing either.
I don't normally use this expression, but since it fits: 'Just do it'. The phrase I've uttered more than once about this stuff is: "This is FM".
