Rosin help please?

Hello,
I made my first attempt at rosin tech today and I had mixed results. I had 2 strains of buds in front of me- Candyland and Birthday Cake- Candyland yielded very well and the other did not yield at all, nothing. My Revlon iron has temp from 310 to 410 and I used the 310 temp setting although I did increase the temp when strain 2 was not yielding and that did not help at all. Both strains seemed very top shelf while i was smoking them. Can i conclude that the Birthday Cake was just not very good quality because it did not yield any rosin, are some strains better than others for rosin and what is the ideal temp for the iron?
 
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