I just wanted to add one more thing to, two otherwise good posts. Naptha will hold ~ 1g/100ml (this was from another thread, I sadly don't have the link)
When SWIM first started out with this, he didn't have much of a life, so a few jars could sit next to him at home as he worked. He would mix (as directed above) but continue to do this all day. Each jar was swirled every 30 mins or so for about 2 hours. Labor intensive I know, but the pulls were great and on the 3rd+ pull, yield was DRASTICALLY reduced (I am assuming because of the re-swirling allowing more solvent absorption because total yield matched to the range it ought to be.)
tl;dr - Try using more naptha and more swirling and if you can, a touch of heat (SWIM uses a small, desktop coffeecup warmer) and you can reduce the amount of time spent pulling and along with half-evapping you are still over-saturating the solution and crystallization has never been a problem.