Lacquer thinner
Offhand I'd recommend DOT 3 (generic) brake fluid. Dirty/used would likely work as well as new, if you were to bleed your car brakes and top off the master cylinder, something I think is beneficial maintenance...
There are tables on the Web showing how long this takes to act, but if stripping I'd just leave it on until the paint softens.
I have a few Mantua aluminum passenger cars where some of the smooth surfaces (along and above the windows) were painted with a stripe of blue or green paint, presumably by previous owner(s). I wish to remove said paint. I do not intend to paint over the same areas, but to leave the bare metal exposed, so I'd like to keep the surface intact (i.e. avoid abrasives). What are my options? What chemicals can be used that will not harm the aluminum?