There are dumber and less-dumb ways to do halfaѕѕed charge-ups of MVAC systems. Using highly flammable compounds in a system not designed or intended to contain them is the (much) dumber way, unless you wanna die in a fire.
Using other-than-appropriate nonflammable compounds is the less-dumb way:
Part I,
Part II. (dude's entire channel is a time-suck if you like watching and learning from people who know WTF they're talking about/doing as they refurbish old obsolete machinery)
Remember, if there is
anything other than a legitimate A/C refrigerant (R12 or R134a) in your system, you are 100% on your own for repairs; no shop you would want anywhere near your car will touch a system with anything else in it, or if they will, it'll come with a hefty