I try to avoid ISO alcohols like the plague. They pick up water very fast and just move grease or fingerprint oils around on the optic. Ethanol does that as well, and cross polymerizes on ion laser optics from the UV.
Methanol and Acetone are the way to go.
Multilayer coatings are almost always somewhat hydroscopic, hence the prohibition on water.
I've never had problems obtaining 1 litre of spectroscopic grade chemicals, by walking into the shop, handing a business card over, and explaining WHY I need the good stuff. Regulators often get requests for deviations, and if your not buying gallons, tend to allow them.
If you can't get better chems, buy the iso and somehow get it distilled in laboratory glass.
Karl, She's retired, she wont be writing optics installation manuals any more. I remember the day you argued with her... That was very brave....
Steve