I like your thinking on the IPA. Don't waste the good stuff on cleaning up. Save it for later.
What I'm getting at is that you have to seal the threads, such as where the fitting screws into the master cylinder. The 'bit with the nut' such as the brake tube end, is designed to seal mechanically. That little brass thingy that we Aussies call an olive, is trapped between 2 opposing tapers. The force of the nut pushing down on it makes it bite into the outside of the plastic line, producing the seal. Assembled correctly, no sealant should be needed.
Similarly the AN 37.5 degree fittings rely on a clean finished taper to make the seal mechanically. No sealant should be needed.
Clear as mud, eh?
Love your tail number, that's what my grandkids call me.
Let's go oilers