if you put your naphtha in the freezer (-20°C) the crystals usually form at the bottom of the jar or on the sides. you might have a few floaters that you will have to catch with a filter, but the majority should be on the glass. Once you decant you just put the glass somewhere upside down with a tilt to it so the rest of the solvent can evap off the crystals. Make sure you have a plate or something underneath it in case some crystals fall down when they dry. Then when you're sure they're completely dry you can scrape them from the bottom and decide whether they're clean enough for you or if you want to reX them ...

if they're white they're prolly good to go but you should decide that for yourself.