The sticky film is likely just some n-n-dmt-oxides, still active like the white but gooey and yellow instead of crystally and white. The hotter the naptha, the more n-n-oxides are pulled.
That being said, SWIM's warm naptha didn't leave a residue, though he has had that before in STB teks.
As for changa SWIM is not experienced but he hears that ISO will work fine.
Cheers and good luck
Q21Q21's Tek: A comprehensive guide to extracting DMTThe 2 teks use non-toxic lime and vinegar and Tek 1: d-Limonene or Xylene or Tek 2: Naptha to produce very quick high yields with the greatest of ease.I am almost never on this site anymore so I will likely not answer PMs