Do the sc wash before you freeze your naptha. You shouldn't need to do any more than 3 pulls if you maximise the first 2.
I would avoiid the filter too, just pour off the naptha after freezing and let the crystals dry. Keep your naptha for future extractions
When you rexcrystallise you can keep the dmt and warm naptha uncovered till it reaches room temp and then cover and fridge and then freezer.
Hope this helps.