a quick look tells me that tek is full if misinformation (this vinyl/plastic need and oxygen melt story, the unnecessary use of deionized water, saying at some point that shaking will ruin the dmt and then later saying to shake when mixing, which increases chance of emulsion, etc). I suggest you check the teks at the
WIKI, they are much more trustable. Everybody was a beginner once, there's a lot of people (me included) which had no previous chemical knowledge but learned a lot just being in the nexus and reading. Once again, check the FAQ, there is an
overview of extraction processes. Read that as well as the teks there linked, read all of them, thats your homework for the next days/weeks, and keep reading this forum, and you'll start understanding muuuuuuuuuuch more.
for the naphtha being removed from the dmt, thats why you are doing what is written in the FAQ. First you pour off the naphtha to remove the majority of it, then you turn it upside down with the lid on to let remaining naphtha drop off the crystals, then you scrape the crystals and put them on an open dish to finish drying (i.e. the small amount of remaining naphtha will evaporate off). This will be what you do to prevent naphtha in your crystals so that you can smoke them.
Just check a dictionary/google to understand what dissolving/dissolution means.