Try talking to Oilmaker68, he is a solid guy and I'll call him an expert. He is around on the forum and should chime in anytime tonight I imagine.
My understanding is he uses 99.9% iso for his extractions.
If you are looking for new seeds, I would suggest a strain called hashplant, it is my understanding that it is great for hash because it's a very heavy trich producer, trichs on top of trichs as I've heard it described.