How you deal with your parents is your business, but I would strongly discourage trying to do this in a ditch somewhere or any other poorly controlled environment. You need a clean, ventilated space where you won't be disturbed to do an extraction safely with things like lye and naptha. This isn't like making hash oil with rubbing alcohol - you're working with a dangerous base (lye) and one of the most flammable materials available (naptha), you're relying on your ability to keep lye water and naptha separate which means if your jar falls down and bumps around a bunch you're pretty much hosed... Make a friend with an apartment before trying this, or wait until you have the house to yourself for a couple days at least, IMHO.
BTW, they weren't telling you to use zippo fluid per se, just that naptha is the primary ingredient *in* zippo and other lighter fluids. Those fluids often have other additives in them, though. IIRC, the naptha sold as paint thinner is typically pure naptha, but make sure to check the packaging to be sure.
At any rate, if you're going through this much trouble to set it up in addition to learning to do your first extraction, it seems silly to do it with only an ounce of MHRB. If you screw up a step and reduce your yield a bit, or just have somewhat low alkaloid content MHRB to begin with, you could easily end up without enough full 50mg doses for 4 people to try it once. It's virtually the same amount of effort to extract from 250g as it is to extract from 25g. You already seem willing to spend a few extra bucks getting whatever the best solvents, etc. are, getting the most appropriate containers for everything, etc., so I can't imagine the cost of a little more MHRB is a huge problem... Source discussion isn't allowed here and overly specific price discussion is frowned upon, I think it's acceptable for me to tell you that if the cost per ounce of MHRB is prohibitive, you are almost certainly getting ripped off. I've never even seen it sold in such small quantities.
