OK folks, I had some time available today so 4 hours went into washing and waxing my old bus, as well as cleaning the windows. I'm loving the results
After my last windshield cleaning outlined above, initially the glass seemed quite clean, but when the sunlight hit it just right I still saw some slight oily streaking. So I tried paint thinner (mineral spirits), but it just spread the streaking everywhere and the soap/ glass cleaner treatment used above didn't help. I tried lacquer thinner, a stronger and faster drying solvent with the same results. Even acetone worked similarly. Next came denatured alcohol (a common fuel fro camping stoves) which did considerably better but there was still some oily streaking. So apparently, thinning or reducing the mess isn't the answer nor it it a good approach as all this stuff is ruinous to plastics. What did work- the dish-washing liquid soap- was going to take many many applications so I decided to use a stronger soap.
I don't know about elsewhere, but in the US we can get some super-strength cleaning soaps under the brand names of "Purple Power", "Simple Green", "Simply Awesome", and I'm sure there are other brands too. Undiluted this stuff can damage the finish of certain plastics and paints. I eyeballed a 33% mix with water and had a go at it again. With a microfiber cloth dipped in the mix, I applied it then wiped dry with paper towels. It seemed to need another round so I did it again. Once around with the glass cleaner almost did the job, another time got it all. You wouldn't believe how much crap was on the cloth and paper towels until the last go with the "Sprayway" glass cleaner- those finished clean. I drove around to let the sun hit from all angles. I peered from inside and out when I got back home. Spotless. I wiped some small areas with damp paper towels and dry, as well as with dry only; spotless and no oily streaking which I'd always gotten before doing this..
Now I know the trick, and you do too
In conclusion here's what I recommend: Being that these cleaners are so strong DO be careful and DO lay something on the dash to catch any drips. And the floor or seats if they might get dripped on. Start with the "Sprayway" glass cleaner; if that's not doing it try dish soap. Only then should you try the super-soaps.
Further thoughts: Solvents do not directly remove oils; they only thin them. They might be effective on non-oily residues or slightly oily surfaces, but with heavy oils and nicotine they only reduce the problem, not eliminate it. What is needed is something that stops the bond between glass and the oil, and that is what these grease-cutting soaps do. Until that bond is broken all efforts will be futile as there will always be some oily residue remaining. I had been using "Liquid Glass" glass cleaner, but it seemed to just bead up on the glass, just like water on an oily surface does. Even without the soap, the "Sprayway" cleaner didn't do that; the foam stayed well-distributed and it did remove some of the oils by itself, just not all of it. It didn't seem to have any affect on plastics which is a good thing, however there is a chance that something is happening but not so much as to be visible to the eye. I've tried all the common glass cleaners and the "Sprayway" beats the pants off of all of them. On thinking it over, if my nicotine had gotten on the glass, then it had to be on my camera lenses too. I used a paper towel dampened with the "Sprayway" and rubbed gently. It didn't seem to hurt but I'll have to look at some vids to be sure.
I DO NOT recommend treating a lens this way. On one rear door glass there were some small water-based acrylic exterior paint spatters. The super-soap etc. treatment and some rubbing took them right off, only the larger ones needed help from a fingernail. On the outside of my windows I applied car wax since especially the back ones get nasty quick;y, and this seems to act much like "Rain-X" so it should help with the rear vids in the rain too. I have a 4K cam under test which I can't yet speak of, but I can only imagine how bad it would have seemed before the glass was cleaned, and even moreso with my old sand-pitted and wiper-scratched windshield. I'll be cleaning on a regular basis as I'm still smoking but at least that should be easier and a whole lot more effective now. And I still have two windows to go, the rear sides behind my shelves- they will get their due when I move the K2S cams back there, but that's for another day. Thinking of Johnny Nash and Jimmy Cliff singing "I can see clearly now"..... because
now I can
Phil